It is located very close to Monastiraki square that is petty good but also a bit noisy the first hours of the night.
The appartment is very new and has lots of technology but it has some problems with it, like lots aod led indicators that light the room at all times (if you need darkness to sleep this could be a problem).
Also, for some reason, the TV turned on at 3am and it woke us up and scared us a bit. I would suggest to unplug it from the light to avoit it.
To sum up, great appartment and host but with some tech troubles.