If you like live theater performances, experience a play at NTNG - Vassiliko Theatro. Check online for times and prices.
You'll have no end of sightseeing choices when visiting Thessaloniki City Centre. NTNG - Vassiliko Theatro is a great place to begin here, but there are lots of other worthy sights to visit. Aristotelous Square, White Tower of Thessaloniki, and Church of Saint Demetrius are close to the arts and culture attraction and and will cap off your day nicely.