Great place right in the city center - barely a five minute walk from Aristotelous Square, which is the city's central square. Nothing is too far, with plenty of great restaurants, bars, and shops well within walking distance (there's even a great little bar right on the corner, you can't miss it). The apartment even overlooks the beautiful Roman Agora, one of the city's main historic sites.
The place itself is well provisioned with a spacious balcony, full kitchen and bathroom, washer, and a comfortable living area with a smart TV, and Alex is incredibly accommodating and was always very communicative throughout my long stay. Highly recommend this place if you're planning on a stay in Thessaloniki, long or short.