Cidadela de Cascais ("Citadel of Cascais") is a historic fortification located in Cascais, built between the 15th and 17th centuries, with the historic purpose of protecting Portugal's coastline as well as its capital city, Lisbon. Today, it is situated right next to the Cascais Marina.

Cidadela de Cascais is home to a luxury hotel, an art gallery (Cidadela Art District), a resturant (Taberna da Praça) and still serves as the summer residence of Portugal's president nowadays.

Make sure you also visit the Cascais Marina and Praia de Santa Marta ("Santa Marta beach"), which are just a few footsteps away from Cidadela de Cascais.