All day in Sintra. First, to the top of the mountain, so you can see:
Pena Palace (includes the Gardens, Chalet Condessa D'Ela and Valley of the Lakes).
The fantastic Palácio da Pena is one of the best examples of 19th-century Romantic revivalism in Portugal. The interior of the palace is still decorated according to the tastes of the kings and queens who lived there.

Moorish Castle, is a privileged viewpoint to admire the view extending from Sintra to the ocean.

Afterwards, the visit goes down and passes in a small town call São Pedro. Here you can take the opportunity to enjoy a meal in a typical Portuguese food Restaurant.

The next stage is the Romantic Gardens.
This route takes you to the mystic Quinta da Regaleira (known for the Inverted Well). Quinta da Regaleira is one of the most enigmatic places in Sintra. Surrounded by lush vegetation, the Palace of Regaleira is a fascinating discovery. The Palace was built in a romantic revivalist style, recovering Gothic, Manueline and Renaissance architectural and decorative forms, mixed with mythical and esoteric symbology.

The last monument in this route is Palace and Park of Monserrate. The palace was designed by architects Thomas James Knowles (father and son) and built in 1858. The construction of the gardens was able to exploit the micro-climatic particularities of the Serra, thus obtaining a magnificent park in which more than 3,000 exotic species can still be observed.

You can end your visit here, or head to the Coast, where you will find three wonderful beaches: Praia Grande, Praia das Maçãs and Azenhas do Mar. You'll find small enclosed places and wide sands and hidden beaches.
It's worth taking a look at some of them even outside the summer period, to see the incredible landscapes of the Atlantic coast. The coast has the particularity of the Mountain joining the Sea.
Sintra's beaches can be truly amazing!