Onondaga Cave State Park is located near the western edge of the eastern deciduous forest biome in Missouri's Mark Twain National Forest. Above ground, you will see the dense, diverse seasonal forests typical of this biome. Below ground is an especially high-quality cave.

"Onondaga Cave is a highly scenic cave because of the great abundance and quality of its cave formations. Stalactites, stalagmites, columns, rimstone dams, cave coral, draperies, flowstone, and soda straws extensively decorate the cave... Massive draperies are intricately deposited and deeply folded, while simply formed soda straws hang by the thousands from the ceiling.

Onondaga Cave represents one of Missouri's finest underground masterpieces and is preserved and interpreted as part of the Missouri state park system. The National Park Service, recognizing the outstanding quality of Onondaga Cave, designated it as a National Natural Landmark in 1980.

Many of the (cave) deposits are still growing with the continued deposition of calcium carbonate. A stream meanders through the cave in its entrenched canyon.

In addition to its geologic diversity, the cave is also home to a great variety of cave animals, including the Onondaga Cave amphipod, first identified in the Lily Pad Room."
- from park brochures