Koza Han, koza meaning literally 'silk cocoon', was founded by Sultan Bayezid II as a waqf (or pious foundation) to fund his imaret in Istanbul.
It was completed in 1491 and was the center of the silk trade for centuries.
In the center of the courtyard is an octagonal kiosk-masjid supported on eight stone pillars connected to each other by arches.
Beneath the mosque is an octagonal fountain with an additional pillar in its center.
The masjid is accessed by a marble stairway and is covered with a dome.
Adapted from www.discoverislamicart.org