Old Nessebar is beautiful, one of the true gems of the Bulgarian Black Sea coast. MPM Hotel Arsena is perfectly located to enjoy it, right on the beach, full sea view, amazing moonlight, and a pleasant 10-15 minutes stroll away from the Old City.
Rooms are large, clean, with large bathrooms and walk-in shower - one minus would be the lack of a shower curtain. Nice balcony/terrace, free wifi in the rooms as well.
The beach is perfect - large, fine sand, no rocks in the water - perfect for kids.
Pool area is very nice too - a bit small so I imagine could get crowded in full season, but the beach is right there to compensate!
Food is quite good - large selection of vegetables, cooked Bulgarian style, quite nice. Large room for improvement, however, is in the deserts department, which leaves a lot to be desired. Also the bar/drinks area in the main restaurant should be reorganized. One coffee machine is not enough and generates queueing. Also the dishwasher - or the lack of it - is a problem. Serving drinks - all drinks - and washing cups and glasses should not be left to the same one person, and in full sight of everyone!
However these are only small hiccups, which could be easily remedied. Overall, this hotel offers a great experience and I would recommend it to anyone visiting the area.