The place is super central, just 200 metres from Syntagma. It is in a pedestrianized street, right in the middle of the tourist attractions, ideal for sightseeing.
Do not expect anything fancy, what you see is what you get, a clean, practical and quite spacious place in a very central location at an affordable price.
Giannis is super easy to communicate with. He works in the poke sushi place at the ground floor (which should be recommended for a fast , tasty and healthy meal).
The place is in a very lifely area, so bring ear plugs when you are a light sleeper.