Pantelis' flat is perfectly located right in the heart of Thessaloniki! It's a 5- or 10-minute walk to the Arch of Gallerius and the Rotunda, and a similar distance in the other direction to the waterfront and the White Tower. The local Masoutis (supermarket) is a couple of minutes' walk down the road.
The flat is beautifully decorated, very clean, and feels homely. It's well equipped and had everything we needed (though be aware there's no microwave if you want to warm up food--only a small oven). We really enjoyed just stepping out on the balcony and absorbing the Thessalonian atmosphere!
Pantelis was lovely and really accommodating, allowing us to check out a few hours later because we had to take a train in the afternoon.
All in all, we can't recommend it highly enough!