If you have even the slightest interest in history, make sure to add Montjuïc Castle to your Barcelona itinerary ... when the threat of invasion from Spanish King Philip IV's fleet became ...

Marked in yellow here is the location of the access to the Morrot tunnels. On the left we see Montjuic Castle, at the top of the mountain, and on the right we see the port of Barcelona (Source: Carta ...