Guaita Castle is a medieval fortification located in the city of San Marino, a tiny landlocked country surrounded by Italy. Guaita Castle is one of the three castles that sit atop the hills surrounding San Marino, and is the oldest and most famous of the three.

The castle was built in the 11th century and has served as a military fortification and prison over the centuries. Today, it is a popular tourist attraction and one of the most recognizable symbols of San Marino. Visitors can climb to the top of the castle and enjoy panoramic views of the surrounding countryside, as well as see the remains of the castle's walls, towers, and other fortifications.

The castle is also home to a museum, which showcases the history and culture of San Marino. The museum features exhibits on the history of the castle, the history of San Marino, and the role of the castle in the defense of the city over the centuries. Visitors can also see medieval weapons and armor, as well as artifacts from the castle's long history.