The last street in Pittsburgh that's paved with wood.

Sections of the iconic limestone columns have been left uncleaned as a reminder of the city's polluted past.

The largest university building in the West is a gothic masterpiece containing dozens of theme rooms based on different countries.

A beautiful oddities shop crammed with strange and morbid curiosities.

When oil was discovered just outside of Pittsburgh, the city became home to this regional stock market.

A restored Pittsburgh house of God has been converted to a marvelous house of suds.

A quiet, gothic haven nestled between Pittsburgh's Squirrel Hill and Point Breeze neighborhoods.

A massive sea stack famous for its appearance in The Goonies.

This historic lighthouse was well known for the large number of women who served as its keeper.

The actual model from the original "Star Trek" series is now on display at the National Air and Space Museum.

The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

The walls of the iconic dome are hollow and have a secret stairway.

Washington's iconic carousel has a nice piece of Civil Rights history.

A lovely aquatic park built by a one-armed Civil War veteran who made a fortune from lotuses.

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

Members of Congress have traveled between the buildings on Capitol Hill for a century hidden from tourists, press, and storm clouds.

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

The 28,000-year-old specimen is remarkably intact.

A muscular Art Deco monument represents the struggle between regulators and unbridled markets.

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

This forgotten boat elevator was an engineering marvel in its heyday.

This sandwich shop has a century-old elevator behind a sheet of plexiglass.

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

Bar full of oddities, specimens, artifacts and homages to the great dime museums of the past.