Two Largest Cave Systems in North America

1. Mammoth Cave System (Kentucky) – World's longest known cave system, >400 miles mapped. Home to bats, cave salamanders, blind fish. UNESCO World Heritage Site.

2. Carlsbad Caverns (New Mexico) – Part of the Sacramento Mountains; >100 caves including the Big Room, one of Earth's largest single chambers. Famous for bat flights and speleothems. National Park.

Both are geological wonders with unique ecosystems and extensive exploration histories.