This massive redwood tree has a hole in the base big enough to drive through.

This conservation area is also home to many of the region's desert tortoises.

When ecosystems collide in the arid Southwest.

Giant, natural amphitheaters made of delicate geological formations called "hoodoos."

See massive fossils that are over 200 million years old in northeastern Arizona.

The deepest lake in the United States, and once the site of epic destruction that lives on in legends.

Once a menacing challenge for trailblazers, this trail is now the most scenic drive in Utah.

The ancient dwellings of the Puebloans, located in the cliffs of majestic mesas.

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

The fifth-longest natural arch in the world, and the longest outside China.

Mysterious ancient boulder carved with petroglyphs in the mountains of Western North Carolina.

This Yellowstone geyser may not shoot as high as the nearby Old Faithful, but it erupts for considerably longer.

Quite simply the largest tree in the world (by volume).

San Francisco's oldest surviving monument and meeting place for 1906 survivors.

Golden Gate Park's historic collection of plants.

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

Relics of the 1894 Midwinter Exposition continue to delight visitors today.

Sky ships, planes, and portraits left as unique tokens of hope and thankfulness.

What if all public housing projects had been designed by "the Pygmalion of modern architecture," not only their prototype?

This modern museum of Mediterranean culture is surrounded by a surreal concrete honeycomb.

This historic island prison holds one of the dungeons from the Count of Monte Cristo even though it is a work of fiction.

The site of a strange super top-secret military experiment during WWII on a remote Canadian lake.

This natural wonder is disappearing at an alarming rate.

Every fall this lake mysteriously drains, like a bathtub with the plug pulled out.