If you have more than a day, abbreviate your first day, so you don't feel obligated to see the city in one fell swoop. You might begin your second day with the Upper City and work your way downhill. Start at Vlatadon Monastery and then head down, stopping at the enchanting little churches of Osios David, Nikolaos Orphanos, and Profitias Elias. Even if church architecture, mosaics, and frescoes are not your passion, you'll walk through the narrow streets lined with two-story wood houses dating back to the Turkish period. If you didn't see them on your first day, take in the churches of Ayia Sofia and Ayios Dimitrios when you get back down to the city center and stroll past the Alatza Imaret and Yeni Hamam Baths, relics of the city's Turkish past.
Then, for a change of pace, take in the city's markets that blur one into another: the Modiano, the open-air food market on Athonos Square, the Kapani (Vlali), and Bezesteni markets. If you visit all these, you can buy anything from a copper bucket for milking sheep to the sheep itself. Along the way, you can nibble on souvlaki, pastry, or whatever seasonal fruit catches your fancy -- and get a bunch of flowers at the Louloudadika (flower market) in a 16th-century Turkish bath, the Yahudi Haman. If you haven't already seen the arch of Galerius, the Rotunda, and the Roman agora, try to take them in during an evening volta (stroll) with frequent breaks along the way at some of Thessaloniki's myriad cafes.
