This image shows the watery and collapsed opening to the cave named Dance Hall Cave. This feature is part of the much larger Maquoketa Caves State Park in Maquoketa, IA.
There is no description on the back of the card.
Caves such as these often were given imaginative names to encourage tourists to view them. It probably takes quite a bit of imagination to see a flooded cave such as this as a dance hall of any sort.
This image likely dates from the 1940s.