Mehmed I was an Ottoman Sultan known for re-unifying the Ottoman lands of Western Anatolia and Rumelia after the Timurid intervention in Anatolia in 1402/804 AH and subsequent divide in power between himself and his two brothers, Musa and Süleyman Çelebi.
H. Inalcik, "Mehemmed I," Encyclopaedia of Islam, Second Edition. http://dx.doi.org/10.1163/1573-3912_islam_COM_0728 [Accessed April 17, 2018].
Yeşil Medrese, "The Green Madrasa," was constructed as part of a multi-functional complex commissioned by Ottoman sultan Mehmed I. Primary sources date the construction of the building to 1419/822 AH.
The madrasa is a square building with a large courtyard at the center. The main entrance is on the north side, through a portal in the form of a recessed iwan. An arcade surrounds the courtyard on three sides. The south side is occupied by a large domed iwan accessed by two flights of stairs that converge on a balcony at its entrance. This room served as the dershane or study hall. The three arcades on the east, west, and north sides of the courtyard give onto smaller iwans flanked by two square cells on either side. On the north side, the iwan is replaced by the entrance portal.
Byzantine columns and capitals were reused in constructing the arcade surrounding the courtyard. The building is decorated with blue and green tiles on the interior of the classroom and on tympana of windows on the exterior.
Ayverdi, Ekrem Hakki. Osmanlı Mi‘mârîsinde Çelebi ve II. Sultan Murad Devri 806-855 (1403-1451), 94-99. Istanbul: Baha Matbaasi, 1972.