The mosque was also called "Aladja" which means colorful , as till 1689, the facade walls and the tambour of the building were decorated with incrustations from ceramic tiles. The founder of the mosque was the well known Sultan's deputy in Skopje, Ishag Bay who was the greatest donor of the Ottoman public buildings from the profane and sacral character in Skopje. This building is the best represent of the developed type of the Boer architectural style of one-dome mosques with sideways enlargements. Over the central nave, there is a dome and sideways there are per one smaller dome. The interior is full with rich decoration in relief and pandantiphs. The massive wooden doors are decorated with geometrical and oriental figures done in shallow carving. Around the Ishag Bay's mosque in XV century it was organized a huge architectural complex with high architectural values which was consisted of inns, public charity kitchen (imaret), Muslim secondary religious school (medresa) and turbeh. The Muslim secondary religious school, one of the most known in Rumelia, was a significant cultural center where great tinkers from those times as Isac Chelebija lived and taught. There they studied the oriental languages, the Islamic law, philosophy and mathematics.Within the framework of the complex, Ishag Bay founded the first library (kütüphane) in Skopje bequeathed to the mosque in 1445.

 

The turbeh was built on an order of Isa Bay(son of Ishag Bay who was the donor of the Aladja Mosque), and it is supposed that here his treasurer (hazinedar) was buried. Isa Bay was buried in his son (Isa Bay's) complex. The base of the building belongs to the closed type of turbehs with dome erected on a tambour. The turbeh was built from perfectly finished stone ( light and dark grey) placed in alternating lines with minimum usage of braces. Every side of the building as well as the entrance and the windows are framed with profiled frames. Besides the rich decoration in stone, the turbeh is characterized by the magnificent faience decoration. The faience tiles in different colours and size, applied to the tambour of the dome emphasize the polychrome aesthetic effects on the facades. Especially interesting is the sarcophagus (tubut) in the middle of the turbeh with two grave spots from marble and grave built up of fired bricks.