Adraga beach is a beautiful small beach. The highlights at Adraga are the restaurant and the caves.
Praia da Adraga is worth a stop for lunch and the caves as well when traveling to Sintra and Cabo da Roca. The caves are accessible at low tide only. It's not a huge beach but gets longer during low tide. In the caves and at the rocks you can spot the typical clams called "percebes". There is a small car park close to the excellent restaurant and a second for a small fee is open during summer. Parking can be an issue during the summer and Christmas holidays.
If you like to eat at the restaurant booking is recommended. Restaurante D'Adraga is pretty popular and offers exceptionally fresh fish. Many locals come here as well. In the summer you can also sit outside.