Aggstein castle, also known as Burgruine Aggstein, is a ruined castle located in the Wachau region of Austria, overlooking the Danube River. The castle dates back to the 12th century and has a long and storied history, having served as a fortress, a residence, and a prison at various times throughout the centuries.

The castle was originally built by the Kuenringer family, who were an influential noble family in the region. The castle changed hands several times over the centuries and was even destroyed during the Ottoman Wars in the 16th century, but was later rebuilt and expanded upon.

Today, visitors to Aggstein castle can explore the ruins of the fortress, which include the remains of towers, walls, and a chapel. There is also a museum on site that showcases artifacts and exhibits related to the castle's history, as well as a restaurant that serves traditional Austrian cuisine.

In addition to its historical significance, Aggstein castle is also known for its scenic location and stunning views of the Danube River and the surrounding landscape. It is a popular destination for hikers, as there are several trails that lead up to the castle from the surrounding villages.