The Quarantine House of Syros is an abandoned stone building complex on the southern part of the. It was built in 1839- 1841 and initially served as quarantine for travelers, so as to protect the locals from the diseases. The buildings are called “Lazaretta”, from the latin name of this kind of service, established in the Venetian territories during the Venetian domination in the Mediterranean Sea.
The first Quarantine House of Syros inwas built right after the establishment of the new town in its position, currently called , but since it was insufficient for the growing needs of the rapidly-developing city, the Bavarian regents decided to build a new one.
The building complex of the Quarantine House of Syros contained a rectangular yard, whose entrance was by the southern side, where a marble plaque is saved since the opening ceremony of the building. There were 32 apartments for the needs of the travelers, all of them with separate kitchen, toilet and fireplace, while in the western ward there were the cuisines and the offices, for the administrative needs. The symmetric façade of the Quarantine House of Syros, offering a view to the sea, had only one floor, while the ends were duplex. Most of the travelers came from Asia Minor, Turkey, Egypt and were obliged to stay there for at least a week.
During the Cretan Revolution of 1866, the Quarantine House of Syros was initially used as refuge for Cretans, later (near the end of the 19th century as jai, while in 1908 accommodated the Lunatic Asylum. Its last use was as jail for political prisoners, during the post civil war years.