Thessaloniki is a typical large Greek city. This means four lane roads across the city center, creative parking and so on.
The city's most prominent landmarks are the White Tower (lovely posted near the sea) and the Ayia Sofia. This church has an imposing front, and quite distinguished interior. The main colours inside are a kind of dark green, black and bordeaux. Somewhat mystique, especially in combination with the scarce glimpses of sunlight that manage to get in.
There are also innumerable small Byzantine churches scattered around the city. Quite often they are hidden behind apartment blocks, or blocked from the view by parked cars. If you've got some stamina and good walking shoes you can visit several of them, and also enjoy their frescoes.