The fountain kiosk of Ahmed III is located on the road to the Topkapı Palace, close to the outer gate, known as Bab-i Hümayun. It was erected by Ottoman sultan Ahmed III between 1728 and 1729/1141 AH in the place of a Byzantine fountain known as Perayton. The architectural features of the exterior reflect a synthesis of traditional Ottoman and contemporary western styles.
The fountain kiosk is a large square block with a wall fountain at the center of each façade and a semi-circular sebil projecting at each corner. The water is supplied from an octagonal pool inside the kiosk, with circulation space around it for kiosk attendants. While the façades are subtly varied in decoration, the size and layout of the fountains is constant. The wall fountains are set inside shallow niches framed by a crowning arch and marble pilasters, with a large collection basin at the bottom of each fountain. Narrow muqarnas niches adorn the sides of each fountain except on the southeast side where they are replaced by doors providing access to the interior. The marble surfaces of the kiosk are carved with floral patterns in low relief.
Two circular steps lead up to the sebils at each corner. Each sebil has three tall windows crowned with multifoliate arches, which are covered with elaborate bronze lattices depicting lilies. The windows are separated by pilasters that are broken into four sections that increase in diameter going from the ground towards the eaves; the sections are separated by muqarnas molding or capitals. Small openings at the bottom of each lattice window allowed communication from kiosk attendant, who distributed water or sherbet from behind the grille, free of charge.
Above the fountains and niches on each façade and sebil are large calligraphic plates bordered with red tiles. Each plate bears stanzas written in 'ta'lik' script of a 14-line poem composed in praise of the fountain and its donor by Seyyid Hüseyin Vehbi bin Ahmed, the chief judge of Halep and Kayseri. It is read clockwise around the fountain, beginning at the northern sebil. The last stanza of the poem is a chronogram composed by Ahmed III. Written in "celi sülüs" style, it adorns the northwest façade, which is differentiated from the other facades with its more elaborate decoration.
The fountain kiosk has a tall ceiling crowned with a shallow pyramidal vault. It has four small turrets at the corners and a large turret at the center, all domed and coated with lead. The roof projects outward, forming large eaves that shade the walls. The wooden ceiling of the eaves is painted in white and decorated with geometric line patterns in low relief and dark colors. Below the eaves, the thick cornice has bands of marble muqarnas and white floral tiles, separated with thin strips of dark blue tiles that accentuate the curved silhouette of the sebil columns.