Øm Abbey was a Cistercian monastery founded in 1172 on a peninsula between the lakes of Mossø and Gudensø, about five kilometres south of Ry. It functioned as a major religious and agricultural centre for three and a half centuries until it was dissolved in 1560 during the Danish Reformation, after which the stone was quarried by locals for building material. The ruins that remain are modest but atmospheric, set in a quiet lakeside landscape.
The abbey museum at the site displays finds from excavations including the grave goods of monks and laypeople buried here. The monastery's chronicles survive and give an unusually detailed picture of medieval religious life in this part of Jutland. The walking path from Ry along the lakeshore to Øm Abbey takes about an hour and is one of the better walks in the area.