The world's longest known cave system.

A Norwegian-born sculptor created these soaring guardian angels at the entrance to Hoover Dam.

A sculpture of the famous photograph stands on San Diego's "Greatest Generation Walk."

A collection of 20th-century automata, penny arcade games, and musical contraptions.

This stoic, if derpy, giant stands as a monument to Oregon's statehood and the novelty culture of yesteryear.

Portlandia is the second-largest copper repoussé statue in the United States.

A roaring, awe-inspiring double cascade of icy water flows through woodland Oregon like something out of a Tolkien novel.

This working class sculpture pounds his hammer all the livelong day.

Activists are fighting to preserve these unfinished highway ramps as a tribute to the citizen revolt that halted their construction decades ago.

Statue of Lenin, from Cold War era Czechoslovakia, now in a neighborhood of Seattle.

From a neon Rapunzel to a bike traffic meter to a street fair color scheme, the most opened drawbridge in the US is a veritable art gallery.

This former coal gasification plant found a curious second life as a popular public park.

In Paris, Texas they have their own Eiffel Tower, it just has a cowboy hat on it.

This historic address is home to the beloved ball and is an almost totally empty building among the most expensive real estate in the world.

This whimsical group of statues is a favorite of children who love to climb all over Lewis Carroll's beloved characters.

An artist's cute bronze subway sculptures belie his violent artistic past.

Elevated freight railway turned wildly successful urban park.

The highest point in Washington state is a volcano covered in glaciers.

An elaborate gift from Claus Spreckels is now a piece of San Francisco history.

This concrete tangle of square pipes has stood as a proud thorn in the city's side since the '70s.

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

San Francisco's newly reopened hands-on science museum.

Dedicated to the history of the health sciences.

A mythical chimera first sculpted in 1936 as a mix of the main animals of Texas livestock.