Insider Tips: Where to find Portugal's most picturesque castles -

Portugal is studded with amazing castles. These centuries-old buildings, many in an excellent state of preservation, are unique reminders of an earlier age when the nation was under constant threat from external forces and unfriendly neighbors. But where in the country can you find the most scenic strongholds?

Browse this gallery and lay siege to some of the most picturesque castles in the land.

© Shutterstock

Guimarães Castle - Located in the northern city of Guimarães, this 10th century castle is a national landmark, and is considered the birthplace of Portugal.

© Shutterstock

Silves Castle - Probably Roman in origin, this enormous red sandstone castle, located in the Algarve market town of Silves, was later occupied by the Moors between the 8th and 13th centuries.

© iStock

Almourol Castle - This picture perfect medieval castle is perched on top of Almourol islet, in the middle of the Tagus River, near the village of Vila Nova da Barquinha.

© iStock

Monsaraz Castle - The sturdy walls of this 12th century hilltop castle enclose ancient Monsaraz, one of the Alentejo's prettiest towns.

© Shutterstock

Santa Maria da Feira Castle - A fine example of medieval military architecture, this well-preserved castle is found in Portugal's Aveiro district.

© Shutterstock

Marvão Castle - Standing in the Alentejo near Portugal's border with Spain, Marvão Castle dates back to the 8th century.

© Shutterstock

Penedono Castle - The lichen-covered walls of this imposing castle give it a weathered look that befits its long history. The medieval town of Penedono is located in Portugal's central northern reaches.

© Shutterstock

Óbidos Castle - The already picturesque town of Óbidos, with its whitewash cottages and terracotta roofs, is further enhanced by this little gem of a medieval castle.

© iStock

Mértola Castle - Mértola is classified as a museum town. Its 13th century castle is the icing on the cake.

© iStock

São Jorge Castle - Lisbon's landmark castle is also one of the city's most popular visitor attractions. Views from the sturdy ramparts are simply jaw-dropping.

© iStock

Bragança Castle - Located in the far northeast of Portugal, Bragança is noted for its brooding granite-stone castle, which forms part of the 13th century citadel. (Photo: Wikimedia/CC BY 2.0)

© Wikimedia/Creative Commons

Belmonte Castle - Situated near the city of Covilhã in the country's Beira Baixa district, Belmonte dates back to the 12th century.

© iStock

Leiria Castle - The city of Leiria is noted for its impressive 12th century castle, which encloses a former royal palace.

© Shutterstock

Loulé Castle - Known for hosting one of the busiest and most colorful markets in the Algarve, Loulé is equally celebrated for its well-preserved 13th century castle.

© Shutterstock

Alegrete Castle - Set near the Alentejo town of Portalegre, this near-ruined defensive structure once served as an important lookout post across the vast plains stretching towards Spain.

© Shutterstock

Evoramonte Castle - The Alentejo village of Evoramonte is dwarfed by the unusual rectangular shape, and circular towers, of the 12th century castle built to defend the community.

© Shutterstock

Montalegre Castle - This castle is located in northern Portugal. It sits on a hill overlooking the peaceful town of Montalegre in the Vila Real district.

© Shutterstock

Barcelos Castle - Little remains of the castle palace walls that mark the original entrance to this historic northern Portuguese city.

© iStock

Lindoso Castle - The stone used to build this 13th century stronghold is the same as that used to construct the unusual coffin-shaped structures set near the entrance.

© iStock

Tomar Castle - Tomar Castle forms part of the magnificent Convent of Christ complex, a UNESCO World Heritage Site.

© iStock

Sabugal Castle - Standing near the Côa River in central Portugal is this compact and handsome-looking castle, unusual for its pentagonal build.

© Shutterstock

Sortelha Castle - Sortelha is one of the oldest and most beautiful towns in the country. Its medieval veneer is enhanced by the remains of a 12th century castle. (Photo: Wikimedia/CC BY 2.0)

© Wikimedia/Creative Commons

Numão Castle - Vestiges of the remote Numão Castle can still be admired, but you'll have to journey north towards Vila Nova de Foz Côa to admire what's left. (Photo: Wikimedia/CC BY-SA 3.0)

© Wikimedia/Creative Commons

Castle of the Moors - The Moorish castle in Sintra is set along a meandering granite escarpment high above the town, which is located northwest of Lisbon. The whole landscape is a designated UNESCO World Heritage Site.

© Shutterstock

Montemor-o-Velho Castle - One of Portugal's most expansive military landmarks, the castle and its walls afford impressive views across this area of central Portugal. (Photo: Wikimedia/CC BY 2.0)

© Wikimedia/Creative Commons

Marialva Castle - The town of Mêda, in the central eastern district of Guarda, is the setting for this ruined but still alluring stronghold.

© Shutterstock

Campo Maior Castle - Like so many other fortifications in the region, the 13th-century castle at Campo Maior in the Alentejo is orientated towards Spain as a first line of defense.  (Photo: Wikimedia/CC BY-SA 3.0)

© Wikimedia/Creative Commons

Porto de Mós Castle - Designed in the Romanesque style, this delightful medieval eye-opener can be found near the town of Mós, in the far northeast of Portugal. (Photo: Wikimedia/CC BY-SA 3.0)

© Wikimedia/Creative Commons

Viana do Alentejo Castle - Set well off the beaten track in the Alentejo heartland, this ornate Gothic structure is characterized by five cylindrical towers.

© Shutterstock

Mourão Castle - Built during the Middle Ages, this castle is named after the sleepy Alentejo village of Mourão. (Photo: Flickr/CC BY 2.0)

© Flickr/Creative Commons