Walking around Thessaloniki, you can trace the civilisations and people that have left their mark on this great city. The Palace, Triumphal Arch and impressive Rotunda (which formed the city’s administrative and religious centre in Roman times) offer an insight into the reign of emperor Galerius Maximilianos in the early 4th century AD. Meanwhile, the Jewish Museum recreates the life of the Jewish community in pre-war Salonica. And don’t forget to visit the former home of Kemal Ataturk, founder of modern Turkey.
Spend as long as you can exploring the narrow lanes of Ano Poli, one of the oldest districts of Thessaloniki, above the modern town. You’ll find numerous attractions, most notably castles and religious monuments: the Trigoniou Tower and Eptapyrgio fortifications, Ottoman monuments, the Vlatades Monastery and the Byzantine churches of Osios David and Agios Nikolaos Orfanos. This is the best-preserved district of the old city, with views of the Thermaic Gulf and (on clear days) Mt Olympus.
Source : https://www.discovergreece.com/