Kalliopi's studio is spectacular. Location is probably most notable. Technically in Psirri but tucked at the border of Monastiraki. You get a bit of both while being within a 15 minute walk from mostly everything, including Syntagma Square in Plaka. There is a terrace bar that's adjacent to her building, but you would only need earplugs if you're going to sleep early on a Friday or Saturday. I didn't have that item but waking up every morning in Kalliopi's north facing corner studio bathed in natural light outweighed one rowdy Saturday. If you love windows, this is for you.
The property is no frills, but has all the appliances for the kitchen and bathroom (hair dryer) you would need. Two air conditioners is plenty. Wifi was strong enough for me to do all my remote activities and downloads. There's also a safe for your sensitive items. No iron and ironing board, but that's hardly a criticism.
Kalliopi herself is a wonderful host. One of the few that've been so personable. She checked in on me daily on my mobile to offer suggestions and answer my questions. Without hesitation I would recommend being taken into her care.