This forbidding castell (castle or fort) dominates the southeastern heights of Montjuïc and enjoys commanding views over the Mediterranean. It dates, in its present form, from the late 17th and 18th centuries. For most of its dark history, it has been used to watch over the city and as a political prison and killing ground.
Anarchists were executed here around the end of the 19th century, fascists during the civil war and Republicans after it – most notoriously Lluís Companys in 1940. The castle is surrounded by a network of ditches and walls (from which its strategic position over the city and port becomes clear).
An exhibition space in several of the rooms of the castle explains the history of the place, with archaeological finds from prehistoric days to its role as medieval beacon and its later days as a strategic bastion. Most interesting (and disturbing) is the exhibition devoted to the imprisonments, trials and executions that happened here. Don't miss the tombstones (some dating from the 11th century) from the one-time Jewish cemetery on Montjuïc.
The views from the castle and the surrounding area looking over the sea, port and city below are the best part of making the trip here. Around the seaward foot of the castle is an airy walking track, the Camí del Mar, which offers breezy views of the city and sea.
From the Jardins del Mirador, opposite the Mirador (Telefèric) station, you have fine views over the port of Barcelona. A little further downhill, the Jardins de Joan Brossa are charming, landscaped gardens on the site of a former amusement park near Plaça de la Sardana. These gardens contain many Mediterranean species, from cypress to pine and a few palms. There are swings and things, thematic walking trails and some good city views.