The usage of eo is somewhat confusing to me with this sentence:
Medus prope Romam est; iam muri Romani ab eo videntur et porta Capena.
The first half is easy, however the second half is confusing to me because I'm not sure what eo is, and also because of the placement of et porta Capena at the end of the sentence. My initial thought was something like, "and from (here) he can see the walls of Rome and the gate of Capena".
Edit: Corrected Roman to Romam.