[1] Reersø features cliffs on its outer western shore and salt marshes on the neck that cconnect it to the mainland.

Reersø is a popular tourist destination, and there are several summer houses in the area.

[2] The name Reersø dates back to 1231 with an original spelling of Rethærsø, meaning Rēthar's island.

[3] The Reersø peninsula was formed by a terminal moraine from the Great Belt Glacier which arrived from the south during the Weichsel glaciation.

The west coast has eroded up to the moraine, leaving a shoreline marked by dunes and cliffs.