Built on the northern bank of the Tagus between 1514 and 1520 as part of the Tagus estuary defence system, the Tower of Belém is one of the architectural jewels of the reign of Manuel I. In the tower as a whole one can distinguish two distinct volumes and military architectural models: the mediaeval keep tower and the modern bulwark which, as it contained two artillery levels, allowed for long-distance cannon firing as well as ricochet shots over the water. The Tower of Belém is a cultural reference, a symbol of the specificity of Portugal at the time, including its privileged exchange with other cultures and civilisations. As a protector of Portuguese individuality and universality, the tower saw its role confirmed in 1983 when it was classified by UNESCO as 'Cultural Heritage of Humanity'.