I recommend to add the check-in instructions to the listing, so we can read those in the email we receive after booking. We received those info via AirBnB messaging system, but probably due to the slow and hectic internet connection we had in Greece, we didn't notice them until we met the host, Aneta.
The studio is good, a little bit small (but probably this is the standard in central Athens). The bathroom is really small, it's challenging to use the sink without splashing the floor. The location is perfect, but if you want to stay more than 1 night probably it's better to look for a larger space.