The Town Hall of Ermoupolis is placed in Miaouli square. Its particular architecture combines the vibe of the classical ancient Greece with the Romanticism of the West and its general style belongs to the neoclassical architectural style, evidently influenced by the German and Italian architects. The central part is made entirely of marble and there is a marble hanging ladder in its interior that leads to the first floor. The meeting room, where the local government meets, has oil paintings depicting King George I and Queen Olga. The Town Hall also hosts the Archaeological Museum of Syros, the Court of Law, the Land Registry, the Public Archives and some other public services.
The museum displays various collections of findings from excavations made in Syros, such as prehistoric finds brought to light in the fortified settlement of Kastri and the village of Chalandriani, consisting in potteries, marble-carving, metal artwork, utensils, weapons and others. There are also some finds from the ancient city of Syros and from other Cycladic islands such as Amorgos, Kythnos, Aegina, and more. Sculptures, grave columns, and inscriptions from the Hellenistic period are also on display.