The Castle of Barcelona is located next to the mountain of Montjuïc, where a viewpoint is also to be found, from which one can contemplate magnificent outlooks of the city.
It is actually a military fort made of three bastions and designed by Juan Martín Zeremeñoa according to the model of the French military engineer Vauban. It dates back from the 18th century and is surrounded by a moat to which you would get through a drawbridge.
The castle has two floors you can visit entirely and the entrance is free of charge (while the entrance fee to the museum costs 3€).
How to get there: subway until Paral-lel stations, connection with the Montjuïc funicular until Miramar Avenue where you have three options: Parc de Montjuïc bus, touristic bus or the cable railway.