Fort of Subserra - Credit: Wikimedia Commons
The Fort of Subserra (No. 1), also known as the Fort of Alhandra, is situated at 142 metres above sea level close to Alhandra in the municipality of Vila Franca de Xira in the Lisbon District of Portugal. Together with other smaller redoubts and batteries that also had the Subserra name, it was built during the Peninsular War (1807–14) as part of the first line of defence of the Lines of Torres Vedras planned by Arthur Wellesley, 1st Duke of Wellington to protect the Portuguese capital of Lisbon and, if necessary, his own retreat. Read more on Wikipedia
Source: en.wikipedia.org