Largest Roman Catholic church in North America.

The remains of Martha, the last known passenger pigeon, serve as a tool to educate about conservation.

At 207 feet, one of the world's longest continuous escalators.

Once home to seven different roller coasters, Glen Echo has undergone many transformations since its founding in 1891.

The semi-reclaimed ruins of this canal were once part of an ambitious plan to reroute the mighty potomac.

This pun was simply waiting to come to life, and one defense contractor made it so.

The remains of a community that was forced to move for a dam that never materialized still rot in this Pennsylvania park.

This historic national park is covered in the stunning ruins of red rock pueblos.

This historic collection of Native Alaskan artifacts was resurrected through a partnership between the WPA and tribal artisans.

Largest lake in Great Britain measured by surface area.

Overlooking a Scottish loch, this beautifully crumbling castle once inspired a poem by William Wordsworth.

A historic freight system that found the true gold rush is in tourism.

Strange red rock formations that have been attributed to a higher power for hundreds of years.

The haunted reputation of these abandoned Colorado train tunnels is probably not helped by the terrifying spiked fence.

A classic gold rush hotel can be expected to pick up some ghosts along the way, and the Golden North is no exception.

Europe's largest prehistoric mound – burial site of a legendary king?

The largest stone circle in the world has ended up bringing up more questions than it has answered.

The true age of this ancient stone circle is unknown, but its stunning vista isn't in question.

Amazing and mysterious Neolithic settlement on Scotland's Orkney Islands.

Possibly the oldest of Britain's ancient henges is also one of its most stark.

Enter the world under the hill at this ancient UK burial chamber.