Most monumental and historical area of Lisbon, was from here that many of the great Portuguese explorers embarked on their voyages of discovery: Henry the Navigator and the first overseas expedition to conquer Ceuta in Morocco, Bartolomeu Dias doubled the Cape of Good Hope, the first voyages of Ferdinand Magellan, Vasco da Gama to discover the sea route to India, Christopher Columbus stopped here on his way back to Europe after the discovery of the New World.
The Monument to the Discoveries is the most significant zone with reference to the discoveries, but you also must visit the great monuments like the Tower of Belem and Jeronimos Monastery.
With so much to see, the Ajuda Palace and its interior are often forgotten, but with the opulence of the popular Coach Museum, is the best place to see the royal magnificence of the 18th century in Lisbon and European royal families.
For short stays there are some coffees housed in traditional houses with attractive exterior along Rua Vieira Porto next to the garden in front of the Palacio de Belem. But the best place to have a drink and eat some sweets is the old Confeitaria de Belém, which serves delicious custard tarts (pastéis de belém) in their rooms, decorated with tiles from the 19th century.
One good suggestion could be to buy some of these delicious tarts, and contemplate the great view to the 25 of April Bridge just in front of the river.
This attractions in Belém justify one whole day, but its good if you don”t go on a Monday, because a lot of this places are closed.