The Ruin Urgiz is a dilapidated hilltop castle in the municipality of Densbüren in the Swiss canton of Aargau. It is located northeast of the village on a narrow steep ridge, at an altitude of 577 m above sea level. M. and about 120 meters above the valley floor. It is not known when the castle was built, but at the latest in the 12th century. The first historically secured owners were the lords of Uriols mentioned in 1277, who had received the castle from the bishop of Strasbourg as a fief. The fief also included the small rule Urgiz with the villages Densbüren and Asp. After 1315, there are no more records of the lords of Uriols, the later owners are not known. The Basel earthquake of 1356 caused great damage. At the latest in 1429, the Effinger family from Brugg acquired the Burglehen. In 1444 the castle passed to the Rätz family from Säckingen, in 1475 to the Hasfurter from Lucerne. In 1502, when the castle had already fallen into ruin, the city of Bern acquired the rule of Urgiz and set up a vigilance there. This was occupied for about three hundred years and was in visual communication with the high commanders on the Homberg at Veltheim and the Gislifluh at Thalheim. 1996/97, the remains of the wall of the castle were uncovered and preserved. Remains of the ring wall and the round tower have been preserved from the castle.