The Lal Qil'a lies along the Jamuna River in Agra, northwest of the Taj Mahal. The fortress that Akbar began in 1565 was constructed atop the foundations of a mud-brick fortress attributed to Sikander Lodi; since Akbar's time, the Lal Qil'a has been added to, renovated and restored many times. However, Akbar is responsible for the use of red sandstone veneer, which gives the complex its characteristic hue. More than five hundred masonry buildings, a microcosm of the city, may have originally been held within the fort complex. These buildings, inspired by the architecture of Gujarat and Bengal, featured trabeated construction and Hindu decorative motifs.

After Akbar, his grandson Shah Jahan carried out the most extensive building projects within the complex, including the Diwan-i 'Am. Between 1628-1637, Shah Jehan rebuilt the three main palace courtyards and introduced white marble and polished stucco to the fort's red sandstone material palette. The fort remained the main imperial residence until 1648, when Shah Jahan shifted his court to Delhi; however, its place in Mughal history continued when Awrangzib took the throne from Shah Jehan in 1658, imprisoning his father in the fort, even building an additional wall (1659-1662) to seal Shah Jehan inside.

As the Mughal empire waned over the eighteenth century, the fort was variously occupied by the Jats and the Marathas for short periods, entering British hands in 1803 with the annexation of Agra. The British used the fort for military purposes, including turning the Diwan-i 'Am into an arsenal. Under British occupation, many of the fort's Mughal structures were destroyed and army barracks erected in their place. However, many of the main palace structures near the river survived. From 1876, the upkeep of the fort's historic buildings came under the public works department, and the beginning of the twentieth century saw a renewal of interest in the fort. Lord Curzon initiated major restorations in the fortress, including the removal of many of the British military additions.

In 1923-24, the Archaeological Survey of India made the southern segment of the fort complex, including the residential palaces and the Moti Masjid, accessible to the public through the south gate. After Indian independence in 1947, the fort was taken over by the Indian army; in the early twenty-first century, a large part of the northern segment still remains under military administration. In 1982, the Lal Qil'a and the Taj Mahal were both designated as World Heritage Sites.

The structures forming today's Agra Fort include the ramparts, the Hathi Pol ("elephant gate"), the Amar Singh Gate and the Akbari Gate, which together form the southern gate, the Diwan-i 'Am (hall of public audience), the Daulat Khana, the Diwan-i Khass (hall of private audience), the Anguri Bagh ("grape garden"), the Shah Burj ("royal tower"), the Aramghar ("sleeping chambers"), the Moti Masjid, and the Akbari Mahal, Janaghiri Mahal, Khass Mahal, and imperial hammam.

The present-day fortification follows the irregular outline of the older Lodi construction: dressed red sandstone walls about 21 meters high with a circumference of 2.5 kilometers, enclose the fort. The walls abut the Yamuna River to the east with a straight line (725 meters in length), then form an irregular arc, protected by a moat, towards the west.

There are two main gate complexes into the fort, both protected by barbicans. Each gate comprises two gates: the inner gate penetrates Akbar’s older wall and the outer gate punctures Awrangzib’s outer wall. On the west facing the city of Agra, the Delhi gate leads to the inner Hathi Pol, originally the main public entrance to the fort. From just south of the Hathi Pol, a 226-meter long market street extends east toward the large Diwan-i 'Am courtyard. At the present (2010), the western gate is used mainly by the Indian army, which still occupies parts of the fort located north of the market street. With the exception of the Moti Masjid, most of the structures open to the public are located to the south of the market street.

The southern gate, which includes the outer Amar Singh Gate followed by the Akbari gate, was originally used by the imperial family and is now the main public entrance into the fort complex. A ramp ascends northwards from the southern gate to the courtyard of the Diwan-i 'Am. This north-south path forms the residential axis of the fort, with a succession of courtyards and palaces running to its east along the river’s edge. In the original layout of the fort, the east-west axis defined the public route, while the north-south axis formed the imperial or residential route, and both routes converged at the courtyard of the Diwan-i 'Am.

Along the residential axis, the southernmost courtyard complexes have survived from Akbar’s reign. These include the (partly preserved) Akbari Mahal and Jahangiri Mahal. To the north of the Jahangiri Mahal are the palace structures known as the Anguri Bagh, the Khass Mahal, and the Diwan-i Khass. In 1628 and 1637 Shah Jahan reconstructed all these palaces, as well as the courtyard of the Diwan-i 'Am. All the courtyards are organized then-contemporary principles of riverfront garden design: they are enclosed on three sides by narrow wings of one or two storeys, while the riverside along the east holds pavilions reserved for royal ceremonies and leisure.

The southern gate, originally called the Akbari Darwaza, was renamed the Amar Singh Gate by the British after an episode at the fort involving the Rajput Rao Amar Singh. It has three consecutive entrance gateways built at right angles to each other. This awkward approach was designed to confuse any attacking force and create tight spaces, too restricted for the use of a battering ram. A simple ogee arched outer gate at the end of the drawbridge punctures Awrangzib’s wall; a second one within (perpendicular to the first) is also taller than the first and is clad primarily in red sandstone with intricate tile work. This gate leads to a courtyard, about 45 meters east-west and 25 meters north-south, where the third and final gate punctures through the northern wall. Tall bastions articulated by arched niches flank the ogee arch gateway here. Remnants of geometric multicolored tile patterns are visible on the lower portions of the bastions, while the unornamented upper niches are clad in red sandstone. These bastions are capped by trabeated pavilions with sandstone piers (rectangular in plan) that connect with an open gallery above the gate. The pavilions are roofed by hemispherical cupolas and protected by projecting stone eaves (chajjas).

A straight ramp, flanked by shear walls for the defensive military advantage, leads north to the Diwan-i 'Am through a gateway in the southern gallery. The courtyard of the Diwan-i 'Am measures 120 meters north-south and approximately 155 meters east-west and is surrounded by narrow single-storey galleries (dalans). The courtyard elevations of these dalans are red sandstone multi-cusped arches supported on rectangular pillars. Their other elevations are enclosed (blind) and currently plastered white. The north and south dalans include red sandstone gateways approximately twice the height of the single-storey galleries. The northern gateway leads to the Moti Masjid; the southern gateway connects to the entrance ramp.

Projecting into the courtyard on its eastern side is the great audience hall, the Daulat-Khana-i-Khas-i-u-Am. This hall, measuring 65 meters north-south and 24 meters east-west, is built on a grid of slender fluted stone columns supporting multi-cusped arches in both directions. The outer colonnades have double arches and columns and are protected by projecting chajjas supported on stone brackets. The Daulat Khana is flat-roofed, and the entire structure is plastered white. The building is open and accessible in all directions from the courtyard, with the exception of its eastern wall, which is shared with the Diwan-i Khass. This wall holds a jharokha, or balcony, from which the emperor would address his courtiers and administrators. This niche-like jharokha is located in the centre of the eastern wall, approximately two meters above floor level. It has three cusped arches on slender columns flush with the eastern wall of the hall, while its inner walls are covered with small arched niches ("chini khana" niches). The walls and pillars of the jharokha are decorated profusely with colorful floral pattern inlays. Generally, the Diwan-i 'Am is organized like a Mughal courtyard mosque, with the mihrab niche in the qibla wall replaced by the emperor’s jharokha, reinforcing his dual status as political and spiritual leader.

The series of palaces and courtyards that form the residential axis of the fort is located southeast of the Diwan-i 'Am along the river. While the Diwan-i 'Am was widely accessible, the degree of privacy increased as one moved toward the river, and the riverfront itself was reserved exclusively for the imperial circle. Abutting the Diwan-i 'Am hall towards the east is the Diwan-i Khass, a semi-official palace, while the Anguri Bagh to its south marked the most private area, that reserved for the emperor's court and his family. All of these buildings were constructed by Shah Jahan, while the Jahangiri Mahal and the Akbari Mahal, south of the Anguri Bagh, are the original palaces from Akbar’s reign.

The Diwan-i Khass, now called the Machchhi Bhavan ("fish house"), includes a courtyard measuring 40 meters east-west and 45 meters north-south and surrounded by two-storied colonnades of Shahjahani columns supporting multi-cusped arches. Along the eastern (Yamuna) edge, the upper story of the colonnade breaks to form a river-facing terrace flanked by the Diwan-i Khass pavilion to the south and the Hammam (royal bathhouse) to the north. The Diwan-i Khass pavilion is a two bay structure clad in white marble. Of its bays, the first, called the "iwan," is a pillared hall facing the terrace with multi-cusped arches on slender marble columns. The inner bay, referred to as the "Tanabi Khana," can be entered through five equally spaced ogee arched openings supported on rectangular columns. The surfaces of the columns are articulated with shallow niches, while each archway is topped with an opening covered with an intricate stone jali screen. The roof of the building is flat, and includes a particular detail inspired by the traditional Bengali roof: the roof-wall intersections are slightly rounded and plastered.

To the east of the Diwan-i Khass, the Shah Burj (royal tower) projects towards the river from one of Akbar’s red sandstone bastions. A white marble structure with an arcaded front towards the river and more solid edges, it is decorated with small shallow niches facing west and crowned by an octagonal pavilion ( chattri) with a copper-gilded domed roof. The chattri features alternating red sandstone and white marble panels with openings and jalis, and it was here that the emperor would have his most private meetings with the highest dignitaries, family members, and historians.

To the south of the Shah Burj is the Anguri Bagh ("grape garden"), built by Shah Jahan in 1636. The garden measures 40 meters east-west and 45 meters north-south. Narrow double-storied buildings border it on the north, south and west, and its eastern edge contains the three marble structures of the Khass Mahal (special imperial palace). Designed as a traditional rectangular chahar bagh, the garden is divided by marble walkways which intersect in the centre to form a marble pool. The four cultivated quadrants have interlocking dividers made of slender red sandstone sections laid out is repetitive geometric patterns. The double storied buildings are a succession of open pillared verandahs and small-enclosed rooms (hujra). The upper story has a continuous balcony supported on stone brackets and protected by a red sandstone jali parapet. These buildings, considered to have been the zenana, or residences of the imperial women, have undergone several alterations over time.

The Khass Mahal consists of the central Aramghar (sleeping chambers) of the emperor. It is flanked on either side by identical buildings with curved Bengal roofs; both are also enclosed by walls, designating them as highly private. The southern building was the personal pavilion of Shah Jahan’s daughter Jahanara, while the Bangla-i-Darshan (imperial viewing pavilion) on the north was used by the emperor: his subjects would gather below the fort in order to view him in the pavilion above.

South of the Anguri Bagh is the Akbari Mahal, built by its namesake, and of which very little survives. The better-preserved Jahangiri Mahal is located to its south. Built by Akbar in 1570, the Jahangiri is the only one of Akbar's palace constructions to survive completely intact. One theory holds that the building was so titled after Akbar’s heir, and there is some conjecture that Jahangir used the palace as a residence. However, Jahangir adopted his title only after his accession to the throne. The very private elevation of the building, which lacks openings in the front, and the internal spatial arrangement support the building's use as a zenana, or residence for the imperial women.

The Jahangiri Mahal is faced in red sandstone. Its western elevation contains a central entrance archway set in a deep iwan, flanked by shallow blind arches. Atop this story is a continuous open gallery. Rounded bastions, each with its own domed chattri, are set on either side of the building. The entrance archway leads to a square domed chamber, and then proceeds through an offset private entrance to the central courtyard, around which the spaces of the palace are organized in consecutive bands. The building has a trabeated system of construction with corbelled arches supported on rectangular columns forming colonnaded galleries around the central courtyard. Intricate carvings, which combine Islamic geometric patterns and Hindu motifs such as circular medallions, lotus flowers, and birds, decorate the building.

Some decorative inlay work is present in the buildings from Akbar’s time, particularly in the gate structures. However, it is the Shahjahani architecture within the complex that displays a profusion of pietra dura inlay work set into the white marble structures. This articulation is very similar to that found in the Taj Mahal, and it is possible that the same craftsmen were employed in both projects.

The original aesthetic of the fortress as defined by Akbar was Indo-Islamic, influenced by the architectures of Gujarat and Bengal, provinces at the extreme ends of the Mughal empire. The result was a truly Mughal architecture, a hybrid of Islamic geometric decoration and Hindu motifs over predominantly (Hindu) trabeated structures with small domes present in the chattris.

Sources:

Koch, Ebba. The Complete Taj Mahal. London: Thames and Hudson, 2006. 66-72.

Nath, Ram. Agra and its Monuments. Agra: Historical Research Documentation Programme, 1997. 35-72.

Koch, Ebba. Mughal Architecture: An Outline of its History and Development, 1526-1858. Munich: Prestel, 1991. 53-56.

Peck, Lucy. Agra: The Architectural Heritage. New Delhi: Lotus Collection, 2008. 49-52.

Tillotson, G.H.R. Architectural Guides for Travelers: Mughal India. San Francisco: Chronicle Books, 1990. 71-83.