Dozens of castles and palaces (Palacio da Pena, Castelo dos Mouros, etc.) invite for a day trip from Lisbon or Peniche. To the city center you can easily get by train from Lisbon, to get to the sights you need a local bus or a taxi. Or just book a guided tour from Lisbon.
The beaches of Sintra (Praia Grande, Praia Pequena, Praia das Maçãs and Guincho) are good surfing beaches on those small summer days with out wind.
From Cais de Sodré the train follows the Tejo river to Cascais via the urban beach of Carcavelos and the cultural center Belém, where the original Pasteis de Nata are made. The marina of Cascais is where the rich and famous live and hang out.
Costa da Caparica
Miles of beach of the “Costa”are best to be reached with your own car. There are bus/Metro connection and you can hop on the ferry at Cais de Sodré carrying your surfboard. In July and August all the other 5 million inhabitants of Lisbon do the same.
The only thing to see here is the palace. But when you want to save the €5 highway toll from Lisbon to Peniche, you might as well stop here for a coffee.
Next to Peniche Ericeira is considered Portugal’s second Surf City. The curvy road makes the journey last one hour, but with the right conditions the World Surf Reserve’s reef breaks make up for the trip. Close to ton there is only now beach break. All the other breaks are reefs. A coast line facing pretty straight into the Atlantic makes Ericeira pretty exposed to wind and swell. Good waves are usually only found in fall and winter. But when it’s on it’s on.