Adler Castle resembles the typical mid-European castle of the 15th century. It is the perfect location for the Germans to establish a command outpost in the Alps. The castle has a main keep to the fore of the courtyard above the gatehouse. A smaller keep is located towards the rear face of the castle. The open courtyard serves as the arrival area of vehicles, and a large room on the east side of the castle serves as a warehouse for all supplies. On the upper level on the west side is a large command room above the arcade. The main keep is also a secure area for the storage of top secret documents, maps and information.
Numerous valuable painting previously belonging to wealthy Jewish families of Austria have been stolen by the Nazis and stored in Alder Castle. These paintings are stored behind secret doorways somewhere in the halls of the castle, along with gold, wine and other valuables.
A British intelligence agent, Elizabeth Salter, has infiltrated Adler Castle and located top secret identification documents of high ranking Nazi party and SS officials. A British SAS team was dispatched to infiltrate the caste a second time, make contact with Salter, steal the identification documents, and then escape the castle.
The castle's appearance was modeled after the real Corvin Castle in Transylvania, Romania.