There are a lot of monumental wall inscriptions inside the mosque, to be exact there are 192. The inscriptions are written by the famous Ottoman calligraphers lived in the late 1300s, when the mosque was built.

Closer looks of the Islamic calligraphy. Wikipedia states that the mosque has one of the greatest examples of Islamic calligraphy in the world.

There is also a fountain inside the mosque where worshipers can perform ritual ablutions before prayer. 

How the ceiling looks like. There are a lot of small windows at each dome, from where the lights can come inside the mosque.

You can really feel the peaceful atmosphere inside the mosque. 

The Grand Mosque of Bursa is located in the old city centre of Bursa on the Ataturk Boulevard.