The mihrab is a specially decorated niche in the wall of a mosque indicating the direction of Mecca. Some tombs have them as well. This one belongs to the Yeşil Türbe, or Green Tomb, of Mehmet I Celebi (1382-1421), in Bursa. Though the tomb dates to 15th century, it was heavily damaged in the 1855 earthquake and sources say that “most of the tiles were replaced” subsequently.
I have not been able to discover whether the current decoration of the mihrab reflects in any way the tilework which was there originally. The tile colors and patterns are different from anything you will ever see in Iznik; and while upclose some of the work seems crude, from a distance of a few feet, the result is phenomenal: it is hard to leave the tomb; at night one wakes up thinking about what it was like to stand in front of it. Note that the mihrab is a subtly three-dimensional work: in addition to the (obvious) honey-comb niche, the whole work consists of gently curving surfaces.
It’s hard to stop oneself from hypothesizing — Hegel-like, historiosophically — that all the colors of a city have something in common, some common note, or accent, or flavor; and that they express somehow the character of the people of the city.