Complex sentence: There are four connections with metro Line B: one at Policlinico, and three on the stretch Piramide-Circo Massimo (Rome Metro)-Colosseo, where line 3 follows Metro B on the surface.
Split into simpler sentences: There are four connections with metro Line B, at Policlinico, Piramide, Colosseo and Circo Massimo (Rome Metro). Between Colosseo and Piramide, line 3 follows Metro B on the surface.