The cable-car is the most interesting way to reach Castell de Montjuïc (Montjuïc castle) and the rest of the sights on Montjuïc hill. It starts from Avinguda Miramar where it connects with the funicular railway from Parallel metro station. It's made up of four cabins that give you fantastic views along the way of both the port and the hill itself, especially on sunny days. You can take it both ways.