"A UNESCO World Heritage site, Belém Tower was built on the northern bank of the Tagus River between 1514 and 1520 by architect Francisco de Arruda. Also known as the Tower of St. Vincent, it was originally constructed to defend the city. Later, the fortress acquired new life as both a lighthouse and customs office. No need to be a history buff to enjoy the power of this place. Beware the narrow stairs, though—navigating the building’s five floors and rooftop terrace requires stamina, but the trek to the top is rewarded with killer views." - Alia Akkam, Chadner Navarro