I stayed last weekend at
- Westin Excelsior
The next subway is at the bottom of Via Venetto. You've to walk downhill for about 5 min. The Marriott Grande is one block further.
- St. Regis
Next to a subway station. (5min walk to the main station.)
- Walking distance to the old city (Forum Romanum) is about 15-20min from all hotels.
- Subway to old city (Forum Romanum): you have to change the subway at the main station from all hotels.