The mosque, also known as Gazi Süleyman Pasha Mosque, is the mosque of the conquest of Izmit. With the conquest of Nicomedia in 1332, it was built by Şehzade Gazi Süleyman Pasha in the name of his father, Orhan Gazi, and became the first mosque in the region. Continuing the tradition of the conquest of the Ottoman Empire, Friday sermons are still delivered with swords in the mosque. Orhan Mosque, whose construction epitaph has not survived, has the title of being the first mosque built in the region after the conquest of Izmit and has survived to the present day. The Orhan Mosque, which has been standing for about 690 years, has a flat wooden roof and is accompanied by a plane tree, which is thought to be 700 years old and located in the garden of the mosque. The mosque, which was damaged due to lightning strikes and earthquakes, was restored in 2017 in accordance with its original form.