Southwest of Kirchdorf on the island of Poel are the remains of a fortress. It was a two-part complex built from 1614 to 1619, consisting of a rampart around a church and the immediately adjacent star-shaped fortress.
The earthen ramparts of the fortification system are of impressive size. The water ditches in front are recognizable as reed zones. The fortress is one of the best-preserved early modern fortifications on the German Baltic coast. The redoubt was built by Duke Adolf Friedrich I according to plans by the master builder Ghert Evert Piloot from Emden. It was a Swedish crown estate for a long time and was eventually badly damaged during the Thirty Years' War and fell into disrepair in the following years. The buildings were demolished piece by piece in the 19th century. Only the village church remained as a brick building. A model of the old fortification can be seen in the Kirchdorf Island Museum.