fortress sentinel and gulls

during Napoleonic wars -Portugal was the only continental ally of England and thus 1st-rate candidate for a French invasion- three defensive lines around the capital were built.
This fortress was the last one; it is situated some 12 km W of Lisbon.
Needless to say, Napoleon's victorious troups, in spite of losing some battles on the road (namely, in Bussaco), entered Lisbon , sacked the city, and stayed...this fortress was useless.
Today, on windy days (and there are aplenty windy days on these Atlantic shores), you can see seagulls flocking there, taking a break from the harsh wind. And lots of sun-lovers too