The central railway Station of Rome. It can be reached via the two underground railway lines or a lot of different bus lines stopping at the square facing the station. Opening hours are from 4AM to 1AM. The station is actually one of the more impressive buildings in the city, even though it is not exactly the oldest one there. For many backpackers going to Rome, this is the first place you see in the city. A lot of quite cheap hostels/rooms/hotels are present both left and right of the main building (more hostels/rooms than hotels to the right (and yes - it makes perfect sense what is left and right once you get there))

Unfortunaltely I was unable to find further info about architectual facts. Stay tuned