The Pena National Palace constitutes one of the major expressions of 19th century Romanticism in Portugal. This National Monument was built by the initiative of D. Fernando of Saxe Coburg-Gotha, who married Queen Mary II, in 1836. Endowed with a very complete education, the future King Fernando II quickly fell in love with Sintra and, when going up the Mountain range for the first time, sighted the ruins of the old Convent of Frades Hieronimitas, originally built by Diogo Boitac in the reign of King John II and substantially transformed by King Manuel I that, when fulfilling a promise, ordered it to be reconstructed, into rock, in praise of Our Lady of Pena, donating it again to the Ordem dos Monges de S. Jerónimo (a monks' order).

When the earthquake of 1755 devastated Lisbon and all the surrounding region, the convent of the Pena fell in ruins. But the Chapel, with magnificent retable in marble and alabaster attributed to Nicolau Chanterene, remained unbroken. These ruins, on top of the steep mountains of Sintra, had astonished the young prince D. Fernando. In 1838, he decided to acquire the old convent, all of the involving fences, the nearby Castelo dos Mouros (Castle of Moors) and some other quintas (villas).

Thus, he gave a beginning to his romantic dream: to reconstruct the old convent and to annex a new part to it for complement of this summer residence of the Portuguese Royal Family. The commission for this rebuilding in Romantic style was given to lieutenant-general and mining engineer Baron Wilhelm Ludwig von Eschwege. Almost the entire Palace stands on spectacular, enormous rocks.

He also thought about ordering to plant an English style park, with the most varied, exotic and rich species of trees. By this, the Park and Pena Palace are seen as from a book of enchanted princes and princesses. The extravagant style of the Palace reminds the visitor of the romantic castle Neuschwanstein built by king Ludwig II of Bavaria (built 30 years later than the Pena National Palace). This imitation and combination of different styles wasn't always successful and often leads to strange contrasts, such as a window in Manueline style next to a door in Moorish style.

The Palace, itself, has a profusion of styles and the volume movement has an unusual architecture. The mixture of eclectic styles that exhibits (neo-Gothic, neo-Manueline, neo-Islamic, neo-Renaissance, among other styles) and the references to prominent Portuguese buildings (such as the Belém Tower) are all intentional (in the 19th century people used to like the exotic and romantic).

The set of the diverse sentry boxes, of the most varied forms and shapes, the uneven terraces covered with tiles in neo-Hispanic-Arabic style, are remarkable elements. The notable figure of the Triton symbolizes, according to some authors, the Creation of the World.

The interiors of the Pena Palace were adapted to serve as the Summer residence of the royal family. It has amazing stuccos, painted walls in trompe-l'oeil and various revetments in tile from the 19th century, forming part of the numerous royal collections.

Today, the Pena Palace is open to the general public and is part of the World Heritage Site that is the Cultural Landscape of Sintra.