The official atomic museum of the United States explores the explosive and productive history of a much maligned energy source.

This pseudo-steampunk weapons facility is the world's largest wood and glue structure, and packs quite a wallop.

Scattered around Atlanta are little doors with big charm.

An enormous pink granite batholith, long attributed with spiritual powers by the Tonkawa Indians.

An emerald-green grotto just a short trip from Austin.

The world's second largest single-dish radio telescope, once used to contact E.T.

This limestone cave offers an incredible view of the Río Grande de Arecibo valley.

The highest peak in Puerto Rico is home to a rare fern that can only be found on six trees at its summit.

Central America's deepest lake is actually a volcanic caldera, surrounded by three volcanoes.

An enormous, 30-story-deep hole in the middle of Guatemala City.

This niche museum devoted to ancient religious artifacts is shaped like the very thing it displays.