This historic cliffside mansion uses a natural cave for air conditioning.

These pink granite water slides are the result of millions of years of erosion.

One-of-a-kind preserved ruins of an abandoned 1880s church in Chicago's Pilsen neighborhood.

This historic house museum that celebrates one of the world's most influential social reformers is also one of the most haunted locations in Chicago.

A big museum full of little worlds.

The "World's Largest Underground Business Complex," a 55,000,000-square-foot city underneath Missouri.