Longest road tunnel in the world features an air treatment plant and the illusion of daylight.

A preserved oak tree about 3,500 years old found in Riga, Latvia.

Walk 2,300 feet above the ground on the "Troll's Tongue."

A thin pane of glass keeps visitors from sliding off this futuristic skywalk.

A treasure trove of artifacts, books, and artwork from the "golden age" of exploration.

A self-made museum in Queens, New York continues to display the work of a sculptor known for paving his own way.

Lehigh Valley barge No. 79 still gets tugged along - but now it houses a museum and unusual performances.

Brooklyn vintners creating world-class wine in a city not known for its vineyards.

Four cars from the old system were once on display, but were removed in 2014.

Great place to have a drink and a bite to eat in an atmosphere laden with New York's Bohemian past.

This sculpture by artist Fritz Keonig survived the 9/11 attacks and now stands as a monument to the victims.

Elevated freight railway turned wildly successful urban park.

Blighted Irish field and the ruins of a 19th-century cottage on the edge of urban Manhattan.

World Trade Center memorial likened to a woman's sexual organ.

An old hill fort covered in over 100,000 crosses is a symbol of Lithuanian nationalism and beliefs.

Behind a bodega is a small museum of relics and ephemera showcasing the history of New York.

A modern addition to the Greenpoint skyline.

Nature and beauty amidst pollution and industrial wreckage.

A drawbridge named for a potentially intersex Polish national who fought alongside George Washington during the American Revolution, and an example of "Pulaski Red".

The final resting place of soldiers' loyal canine companions.

The gorgeous library at Trinity College is home to remarkable treasures of Irish identity.

Perfectly preserved ancient monastery in an impossibly dramatic location on a rocky island in the Atlantic.

Twice a year, visitors can tour the desolate site that birthed the Atomic Age.

Twenty-seven massive radio antennas on the high plains of New Mexico search for life on other planets.