The rocks of a certain area of Butte, Montana give off a musical ring when hit.

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

A beautiful geyser under environmental threat.

One man's ambition created this psychedelic log home.

A hidden tunnel of bones in one of Malta's oldest churches.

This eccentrically decorated palace is replete with grottoes, fountains, tunnels, and caves.

This Industrial Age architectural and engineering gem helps visitors and residents alike traverse Lisbon, “The City of Seven Hills.”

Old Danish castle immortalized in Shakespeare's Hamlet.

This striking royal residence is the largest Renaissance-style castle in Scandinavia.

A 19th-century subterranean reservoir repurposed as a contemporary art cave.

A collection of noses tucked inside an art museum reveals how times have changed.

The art museum is decorated with creatively remodeled pre-Nazi swastikas.