I learned that the Elbe Sandstone Mountains in the Sächsische Schweiz National Park are not really mountains! The sandstone formations that make up these "mountains" used to actually be the bed of a sea during the Cretaceous period. This period in earth's history ended 66 million years ago, so the sea has been gone for a long time. After the sea dried up or drained away, these tall standstone layers remained. The standstone "mountains" we see today in the national park are actually these standstone layers that used to be underwater.
