The check-in is done in a building near the apartment, where you pay the 3.5€ per person per night (city tax). Then, you are accompanied to the apartment by a staff member. The room is in the 4th floor (the lift is small, 2 people, but very quiet). The room is clean and with windows at both sides, letting the air flow. The private bathroom is small but functional, with all the utilities. Also, there is room service if you stay more than one night.
The apartment is located 10 minutes walking from the train station and 10 minutes from the colosseum.
Al in all, a very pleasant experience.