Castle of Carlo V, Lecce, Salento, Apulia, Italy

Norman Swabian Aragonese Castle, Monte Sant'Angelo, UNESCO, Foggia, Apulia, Italy

De Monti Castle (Castello de Monti), Corigliano d'Otranto, Lecce, Salento, Apulia, Italy

De Monti Castle (Castello de Monti), Corigliano d'Otranto, Lecce, Salento, Apulia, Italy

Defensive walls ramparts at entrance to Berat Castle UNESCO World Heritage Site, Berat, Albania, Europe

Medieval stone tower on a hill with a clear blue sky in the background, Clifford's Tower, York, North Yorkshire, England, United Kingdom, Europe

Ruined Castle (Cromwell's Barracks), used by pirates Don Bosco and Grace O'Malley, Inishbofin Island, Connemara, County Galway, Connacht, Republic of Ireland

Ogmore Castle near Bridgend, South Wales, United Kingdom

View of Castle of Gjirokastra, UNESCO World Heritage Site, Albania, Europe

View of Hiroshima Castle, with museum, reflecting in Moat, Motomachi, Naka Ward, Hiroshima, Honshu, Japan

Jabrin (Jabreen) Castle (Fort), Ad-Dakhilīyah region,Sultanate of Oman, Arabian Peninsula

Leeds Castle near Maidstone, Kent, England, United Kingdom, Europe

Leeds Castle near Maidstone, Kent, England, United Kingdom, Europe

View of Hiroshima Castle, with museum, reflecting in Moat, Motomachi, Naka Ward, Hiroshima, Honshu, Japan

Aerial of the Guimaraes Castle, UNESCO World Heritage Site, Guimaraes, Norte, Portugal, Europe

Bamburgh Castle, Northumberland, UK, in glowing light at sunset.

Henry VIII's Fort at Pendennis Castle, a fortress that has protected Cornwall from invasion for 450 years, Falmouth, UK.

Dunstanburgh castle on Northumberlands coast near Craster.

Pendennis Castle, a fortress that has protected Cornwall from invasion for 450 years, Falmouth, UK.

Pendennis Castle, a fortress that has protected Cornwall from invasion for 450 years, Falmouth, UK.

Henry VIII's Fort at Pendennis Castle, a fortress that has protected Cornwall from invasion for 450 years, Falmouth, UK.

Dunstanburgh Castle near Craster in Northumberland, UK.

Dunstanburgh castle on Northumberlands coast near Craster.

Dunstanburgh Castle, Northumberland, UK.

Dunstanburgh Castle, Northumberland, UK.

Caerlaverock Castle in Dumfries and Galloway, Scotland, United Kingdom, Europe

El Castillo, Pyramid of Kukulkan, Chichen Itza Archaeological Site, Chichen Itza, Yucatan State, Mexico

El Castillo, Pyramid of Kukulkan, Chichen Itza Archaeological Site, Chichen Itza, Yucatan State, Mexico

View over illuminated roof deck of restaurant Hotel Stein to old town with Salzburg Cathedral, St. Peter's Archabbey, Franciscan Church, City Hall Tower and Hohensalzburg Fortress, largest, fully-preserved fortress in central Europe, in the evening, Salzburg, Salzburg, Austria, Since 1996 historic centre of the city part of the UNESCO World Heritage Site

Hohensalzburg Fortress, largest, fully-preserved fortress in central Europe, Salzburg, Salzburg, Austria, Since 1996 historic centre of the city part of the UNESCO World Heritage Site

Members of the Asian Youth Orchestra smiling at camera, Mirabell castle and garden, Hohensalzburg Fortress, largest, fully-preserved fortress in central Europe, in background, Salzburg, Salzburg, Austria

View over Old Town with Hohensalzburg Fortress, largest, fully-preserved fortress in central Europe, Salzburg Cathedral, Franciscan Church, St. Peter's Archabbey and Collegiate Church, built by Johann Bernhard Fischer von Erlach, Salzburg, Salzburg, Austria, Since 1996 historic centre of the city part of the UNESCO World Heritage Site

Preserved Tiger in Egeskov castle, Wall Decoration in the Hunting Room, Egeskov Slot Castle, Near Kvarndrup, Fuenen, Denmark

View over illuminated roof deck of restaurant Hotel Stein to old town with Salzburg Cathedral and Hohensalzburg Fortress, largest, fully-preserved fortress in central Europe, in the evening, Salzburg, Salzburg, Austria, Since 1996 historic centre of the city part of the UNESCO World Heritage Site

Hohensalzburg Fortress, largest, fully-preserved fortress in central Europe, Salzburg, Salzburg, Austria, Since 1996 historic centre of the city part of the UNESCO World Heritage Site

Wooden targets used by the Belgian army, former NS-Ordensburg Vogelsang (National Socialist estate), Eifel, North Rhine-Westphalia, Germany, Europe

Staircase, former NS-Ordensburg Vogelsang (National Socialist estate), Eifel, North Rhine-Westphalia, Germany, Europe

Ruins of Falkenstein Castle between Neidingen and Thiergarten, one of the best preserved ruins in the Danube Valley, district of Sigmaringen, Baden-Wuerttemberg, Germany, Europe

Medieval castle and church ruins of St. Patricks Cathedral, fully preserved round tower, ornate high cross, Rock of Cashel, County Tipperary, Ireland, Europe

Qasr Kharana, Qasr Karrana, also known as Qasr al-Harrana, Qasr al-Kharanah, Kharaneh or Hraneh, one of the best-preserved desert castles in Jordan

Qasr Kharana, Qasr Karrana, also known as Qasr al-Harrana, Qasr al-Kharanah, Kharaneh or Hraneh, one of the best-preserved desert castles in Jordan

View from the tower of Geyerswoerth Schloss Geyerswoerth castle, Geyerswoerthstrasse 1, on the city, in the left back the St. Michael church and in front the old town hall, Bamberg, Upper Franconia, Bavaria, Germany, Europe

View from the tower of Geyerswoerth Schloss Geyerswoerth castle, Geyerswoerthstrasse 1, on the city with the cathedral left, Neue Residenz palace, in the back the St. Michael church and in the right front the old town hall, Bamberg, Upper Franconia, Bavar

Ruins of Falkenstein Castle between Neidingen and Thiergarten, one of the best preserved ruins in the Danube Valley, district of Sigmaringen, Baden-Wuerttemberg, Germany, Europe

View from the tower of Geyerswoerth Schloss Geyerswoerth castle, Geyerswoerthstrasse 1, on the city, in the back left the Neue Residenz palace, in the upper right the St. Michael church, Bamberg, Upper Franconia, Bavaria, Germany, Europe

Ruins of Falkenstein Castle between Neidingen and Thiergarten, one of the best preserved ruins in the Danube Valley, district of Sigmaringen, Baden-Wuerttemberg, Germany, Europe

Ruins of Falkenstein Castle between Neidingen and Thiergarten, one of the best preserved ruins in the Danube Valley, district of Sigmaringen, Baden-Wuerttemberg, Germany, Europe

Bastions proctecting the Portas de Olivenca. Fort Santa Luzia, the greatest preserved fortification of the 17th century worldwide. Elvas in the Alentejo close to the spanish border. Elvas is listed as UNESCO world heritage. Europe, Southern Europe, Portugal, March

View over the town with the fortifications of Fort Santa Luzia, the greatest preserved fortification worldwide dating back to the 17th century.Elvas in the Alentejo close to the spanish border. Elvas is listed as UNESCO world heritage. Europe, Southern Europe, Portugal, March