The town of Castel del Monte is one of 54 UNESCO World Heritage Sites in Italy and definitely one of the most picturesque towns near the Gran Grasso e Monti della Laga National Park. The castle (already visible from afar, see picture) was built in the first half of the 13th century and a permanent seat of Frederick II of Hohenstaufen, who at the age of three (!!) became sovereign of the Kingdom of Sicily. The castle's architecture is very unique and a perfect example of complex medieval military structures. Its shape is octagonal and it was built with amazing precision. Thankfully the castle was meticulously restored and is open to visitors. Views from the top are fantastic!