The Ulu Camii has a central cupola that lets in lots of light, giving the whole building a sense of openness and space. Under it is an ablations fountain which in a way is awkward (sometimes I have the feeling this is a religious bathhouse), but on the other hand makes the building very special and joyful.

The large fountain (‘şadırvan’) where worshippers can perform ritual ablutions before prayer; it lies quite centrally in the mosque’s interior. It has sixteen sides (and thus sixteen stools placed around it) and was built around 1660, commissioned by Kara Çelebizade Abdülaziz Efendi, who was an important Ottoman state official and the 33th ‘Şeyhülislam’ (the highest rank in Ottoman authority in the issues of Islam).
The access to the square area around the fountain (delineated by the low wooden balustrade) is prohibited for women.

Correspondent: J.M.Criel, Antwerpen.
Sources: Webside of ‘bursaulucamii.com’ & Wikipedia.