Castel del Monte, octagonal castle, built for Emperor Frederick II in the 1240s, UNESCO World Heritage Site, Apulia, Italy, Europe

Castel del Monte, octagonal castle, built for Emperor Frederick II in the 1240s, UNESCO World Heritage Site, Apulia, Italy, Europe

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

Castel del Monte, Apulia, Italy, Europe

Nossa Senhora de Monte Serrat Fort, Salvador, State of Bahia, Brazil, South America

Castel del Monte, UNESCO World Heritage Site, Apulia, Italy, Europe

Castel del Monte on top of a hill surrounded by trees, aerial view, UNESCO World Heritage Site, Apulia, South of Italy, Italy, Europe

Man admires the octagonal castle of Castel del Monte in a clear sunny day, UNESCO World Heritage Site, Apulia, South of Italy, Italy, Europe

Castel del Monte, UNESCO World Heritage Site, among poppies on a sunny day, view from below, Apulia, Italy, Europe

Aerial view of the white octagonal castle of Castel del Monte rising in the middle of the countryside, UNESCO World Heritage Site, Apulia, Italy, Europe

View from below of the octagonal white castle of Castel del Monte, UNESCO World Heritage Site, Apulia, Italy, Europe

Detail of the side facade of the octagonal castle of Castel del Monte, UNESCO World Heritage Site, Apulia, Italy, Europe

Guard House and cannon at Monte Fort, Macau, China, Asia

Castel del Monte Castle, Hohenstaufen Emperor Frederick II, UNESCO World Heritage Site, Province of Barletta-Andria-Trani, Puglia, Italy, Europe

Castel del Monte Castle, Hohenstaufen Emperor Frederick II, UNESCO World Heritage Site, Province of Barletta-Andria-Trani, Puglia, Italy, Europe

RSM San Marino Monte Titano