The ancient city of Bust on the east bank of the Helmand river in southern Afghanistan was settled as early as seventh century B.C.E. and lived its golden age under the Ghaznavids, who established it as their winter capital in 976. The monumental arch located to the north of the citadel mount (Qal'a-i Bust) was built by Ghurid rulers following their conquest of the city in 1149. Arthur U. Pope, Eric Schroeder, and J. Sourdel-Thomine (member of the French archaeological team at Bust in 1951), have suggested that the arch belonged to a great mosque iwan. Terry Allen, on the other hand, has argued that the arch was built free-standing as part of a ceremonial entrance to the citadel that includes the two large squares whose walls are seen in front of and behind the arch.

The pointed archway spans about twenty-five meters and is flanked by buttresses carved with bands of inscriptions and blind arches. An early photograph of the arch shows a northern buttress crumbled to half the height of the archway, carved with a vertical Kufic band adjoining the arch and two tiers of blind niches separated with horizontal panels of inscriptions. The lower tier in this image features a broad horse-shoe arch, while the upper tier includes twin pointed arches. Both the north and south buttresses were capped above the lower tier of niches during the 1960s restoration, leaving Kufic borders rising alone on either side of the arch. Brick supports were erected inside the arch in the 1970s; the archway is blocked on both sides by brick walls.

The decorative effort of the arch is concentrated on the western façade, which contains the inscriptive bands. The outer surface of the arch is covered a tile or terracotta band of floral arabesques and a band of interlacing geometric motifs -- including pentagrams and Hindu swastikas -- made of tiles encrusted with stucco. Kufic bands to the right and left of the arch contain incomplete segments of a Quranic verse and the foundation inscription, respectively. The arch soffit, which is more than one and a half meters wide, is covered with a tile relief interlacing stars and hexagons filled in with terracotta floral motifs. The exterior of the buttresses were decorated with tiles during the restorations.