Castelo de Sāo Jorge
Castelo de São Jorge is one of the most popular tourist destinations and holds a beautiful vista over the capital. It was part of the battle between the Moors and the Christians in the 1100s which means it is richly steeped in the history of the city. Interestingly, there is a camera obscura periscope in one of the towers which provides the viewer with a unique 360-degree view of the city below the castle.