I just finished a stay at Vieri's very spacious apartment especially for just 3 of us. Located very close to the colosseum, forum and at least 2 metro stops. We only used the metro to get to the Vatican as it really is a walkable city but the metro is easy to use if that's a concern of yours. We loved the walk form the colosseum to the Pantheon area especially at night. The apartment fit our needs perfectly, washing machine was a huge benefit and the apartment also has a well equipped kitchen if you're looking to make any meals at home. Otherwise there are several non-touristy restaurants nearby which were incredible. I highly recommend Vieri's apartment and would gladly stay again.