Lisbon, the capital city of Portugal, has a lot to offer! From an old castle overlooking the spreading city, to beaches and typical restaurants, you can easily spend several days exploring. You absolutely have to try the typical egg tart pastry Pastel de Nata.
In Lisbon we stayed at the incredible Eurostars Das Letras that offered great customer service and useful addresses.
If you have some time, Sintra is worth a trip, especially the town itself and its amazing castles, as well as the beach Praia do Guicho which is famous within the kite-surfing community.
Just go there and explore!