Castel del Monte is a unique medieval castle situated in Andria, a town in the Apulia region of Italy. The castle was built by the Holy Roman Emperor Frederick II in the 13th century, and is considered to be a masterpiece of medieval architecture. The castle is an octagonal structure, and each of its eight sides is exactly 26 meters long.

Castel del Monte is situated on a hilltop overlooking the surrounding countryside, and was designed to be both a fortress and a palace. It is famous for its octagonal shape, its unique and intricate architecture, and its symbolic significance. The castle has a total of eight towers, one at each corner of the octagon, and an additional tower above the entrance.

The castle's interior is also impressive, featuring a variety of rooms and halls that were used for various purposes, such as a chapel, a throne room, and a banquet hall. The interior is adorned with beautiful frescoes and mosaics, and many of the rooms feature elaborate decorations and furnishings.

Today, Castel del Monte is a popular tourist destination and is designated as a UNESCO World Heritage Site. It is widely considered to be one of the most important and beautiful examples of medieval architecture in Italy, and continues to inspire visitors with its unique and intriguing design.