To ascend to Ano Syros, you pass through Vrondado (also spelled Vrondado and Vrontado), with its mix of Cycladic and medieval it's a bit like being transported to another time and place. Its stone walls and cobblestone streets, narrow lanes and many arches resound to your footsteps. And step you will, as there are over 870 steps to climb to its peak. (It's also possible to take the bus.) Vrondado has a fine old Byzantine Church, Anastasis, and excellent tavernas which spread over the steps at night.
At the top of the steps Ano Syros. The main entrance to Ano Syros is an ancient vaulted passageway called the Kamara. Ano Syros is a whitewashed predestrian-only quarter. Catholic since the Crusades, this quarter houses Cathedral of St. George, with its star-fretted barrel roof. Next door is the Center for Historical Studies. Not far below are the Jesuit (1744) and Capuchin (1400) Monasteries. The Town Hall is central with the Historic Archives of the Municipality, and the Museum devoted to the popular composer and exponent of Greek blues, Markos Vamvakaris. Various folklore events take place in Ano Syros, generally during the summer. The main drag is called the Piatsa with tavernas, shops and domiciles.
A 45 minute walk from Ermoupolis is the church of Ag. Dimitrios. All ships coming into port hoot as they pass it. In Dili, just above, is and the ancient Temple of Isis built in 200 BC. Little remains of it or the site across the harbor at Lazaretta where a 5th Century BC Temple to Poseidon once stood. There is speculation that this is the Poseidonia mentioned in The Odyssey.
Syros northern section contains lagoon like Grammata Bay where sailors from classical to Byzantine times found refuge from storms and engraved still visible epigrams in the rocks in thanks. In fact 'Grammata' means just that: letters.
At Halandriani (Chalandriani) on the east coast a trove of grave goods were discovered in 1898 in the 500 tombs of the Bronze Age necropolis. An hours walk north to Kastri, there stands the ruins of an ancient Bronze Age citadel, with walls, six towers and foundations still visible.