Mehmed I Celebi inherited not an empire but the wreckage of one. After Bayezid I's catastrophic defeat at Ankara in 1402, Tamerlane carried the Ottoman sultan back to Samarkand in a litter and let Bayezid's four sons fight each other for what remained. Mehmed won the civil war by 1413, and from then until his death in 1421 he set about restitching the realm. The Green Mosque was part of that project. Construction began in 1412 in the eastern foothills of Bursa, the original Ottoman capital before the conquest of Constantinople in 1453. The vizier Haci Ivaz Pasha, a battlefield commander turned patron of the arts, supervised the build. The 15th-century historian Asikpasazade noted that Ivaz Pasha brought masters and men of skill from foreign lands to help. The Persian, Anatolian, and Timurid hands that worked here left their fingerprints in tilework that no purely Ottoman workshop would have produced.

Step inside and the geometry surprises you. The Green Mosque is built on what scholars call an inverted T-plan, a two-story cube with an extension on its qibla side that creates the cross-shaped layout of central hall flanked by domed iwans on east and west. The vestibule opens up a short staircase to the prayer hall, with marble cubby-holes on each side for slippers, a sign that the floor was once paved. Now it is carpeted. A marble fountain sits in an octagonal pool in the central hall. Light filters down through windows on the qibla wall. Wide corridors framed by reused Byzantine columns, hauled from somewhere and given a new life, run to the corner rooms where small fireplaces wait for winter. Stairs spiral up to the lofts, including the royal box where the sultan could pray separately from the congregation.

What makes the Green Mosque green is the tile. Black-line technique, monochrome underglaze, mosaic, painted terra-cotta relief: scholar Patricia Blessing has documented the unusual variety of methods used in the same building. The colors run from emerald and turquoise to white, yellow, and two distinct purples. Hexagonal wainscot tiles in dark green, overlaid with gold, cover the lower walls. The mihrab niche, twelve rows of muqarnas crowned with two ribbed columns, glitters with intricate patterning. Above it, the inscription crediting the masters of Tabriz appears alongside a couplet from the Persian poet Sa'di. The black-line technique recalls earlier Seljuk work seen in places like the Karatay Madrasa in Konya, but the synthesis at Bursa is something new. Patterns associated with Timurid ceramics from Central Asia mingle with Anatolian Seljuk traditions and emerging Ottoman taste.

When Mehmed I died in 1421, his son and successor Murad II commissioned the Green Tomb, the Yesil Turbe, on the same complex. The mausoleum sits across from the mosque, faced with the same brilliant turquoise tiles that give the kulliye its name. Inside, beneath an octagonal cenotaph, lie Mehmed I and members of his family: his sons Mustafa, Mahmud, and Yusuf, several women of his household, and his nanny. The hammam and the imaret, the bathhouse and the public kitchen that once completed the kulliye, survive only in fragments. The mausoleum now houses the Bursa Museum of Turkish and Islamic Art.

On 28 February 1855, a 7.5 magnitude earthquake struck Bursa and damaged the Green Mosque badly. The Ottoman government turned to a French architect named Leon Parvillee, who had been working in Istanbul since 1855 as a decorator and contractor with deep interest in early Ottoman style. Parvillee directed the restoration that began in 1863, repairing both the structure and the tilework. His sense of how Ottoman architecture should be presented to itself, drawn from years of study, would later influence how 19th-century Ottoman officials thought about their own architectural heritage. UNESCO inscribed historic Bursa, including the Green Mosque, on its World Heritage List in 2014, recognizing the city as the cradle of an empire that lasted 600 years and stretched from Vienna to Yemen. The mosque is open to visitors today and remains an active place of prayer.