The 24m-high mound and lighthouse are of historical interest and are listed.
The lighthouse on Sprogø
The lighthouse from 1868 was built on remains of the old castle dating to 1167, erected by Valdemar the Great. The ruins, which are the oldest dated fortifications in Denmark, have been restored by the National Museum in cooperation with Sund & Bælt.
In 1997, the light in the lighthouse was lit once again, after having been out since 1980. It is of no practical significance to boat traffic.