Opposite the tower is the largest and most important Muslim place of worship in the city, the Sultan Mehmet al-Fātih Mosque, also known as the Great Mosque or Royal Mosque. It was commissioned in 1460 by Mehmet II, the Conqueror, and built from precisely shaped ashlars on the outside and bricks on the inside. Above the portico supported by four columns are three domes, the pendentive dome with a span of 13.5 metres is considered the largest of its kind in the former Yugoslavia. The interior, magnificently decorated with a mehfil, mihrāb, minbar and elaborate 18th-century paintings and ornaments, covers an area of approximately 900 square metres, and the 14x14-metre prayer hall can accommodate 800 worshippers.

During the Turkish-Austrian War, the mosque was converted into a Catholic church, but it was restored to its original function after Austria's defeat in 1690. Extensive restoration work was carried out in the early 1960s, and the 17-metre-high minaret was completely rebuilt after an earthquake and can be climbed via 120 steps.