Burg Kropfsberg, Medieval castle ruin in Reith im Alpbachtal, Austria

Burg Kropfsberg is a ruined hill castle on a ridge above St. Gertraudi in the Inn Valley, at 526 metres. Its three nearly equal-height towers are unique in Tyrol: a free-standing west tower from the first castle, two keeps around a hexagonal courtyard, and a middle tower with only light slits below. A 47-metre-deep cistern lies in the courtyard, and remains of the 16th-century Rupertus Chapel and outer ring wall with bastions survive.

Archbishop Konrad I of Salzburg had the first castle built at the entrance to the Zillertal in the first half of the 12th century; it was first documented in 1286. In 1412 a dispute between Tyrol and Bavaria was settled here, and in 1416 Duke Frederick IV reconciled with his brother Ernest. After the court seat moved to Zell am Ziller in 1592, the castle decayed and was auctioned in 1809.

During the 15th century, the castle served as a diplomatic venue where Tyrol and Bavaria resolved territorial disputes through negotiations.

The ruin stands on a ridge above St. Gertraudi at 526 metres. The gate tower was made habitable in 1850 and renovated again after 1940, but the site has no visitor facilities. The keep was converted into a lookout tower after the Second World War. Parts of the outer ring wall and bastions survive.

The castle grounds extended across 26,000 square meters and contained living quarters for up to 80 people during its peak operation period.