Explore the Museu Nacional de Arte Antiga (National Museum of Ancient Art) next to the hotel. The museum is located within the 17th-century Palácio Condes de Alvor and houses some of the most important works of art by artists from the Portuguese school. There are also collections of religious sculpture and Portuguese gold and silverware from the Middle Ages to the Baroque period. Guests at As Janelas Verdes receive complimentary tickets to the Museum.

Visit the Jeronimos Monastery, a UNESCO World Heritage Site. Built by King Manuel I in 1502 to commemorate Vasco da Gama’s voyage, this Manueline-style monastery exemplifies Portugal’s power and wealth during the Age of Discovery. In 1880, da Gama's remains and those of the poet Luís de Camões (who celebrated da Gama's first voyage in his 1572 epic poem, Os Lusíadas) were re-interred in newly carved tombs in the nave of the monastery's church.

Tour Belém Tower, a 16th-century fortress that once served as a point of embarkation and disembarkation for Portuguese explorers. Constructed between 1515 and 1519 during the reign of King Manuel I, the fortress would become the ceremonial gateway to Lisbon and a prime example of Manueline architecture. In 1983, Belém Tower became a UNESCO World Heritage Site along with the nearby Jeronimos Monastery.