After sitting abandoned for decades, this historic mine is now the only publicly accessible chalk room and pillar mine in North America.

Constrained by time and topography, this civil engineering landmark was constructed 100 feet above Starrucca Creek over the course of a single year.

A natural sandstone bridge nestled within a mature forest in southern Illinois.

This sculpture is a cross between an observatory and an earth mound to honor the community's rich history.

This interactive museum preserves the big aviation history of this small Missouri town

This distinctive bug-like bridge is made of recycled horseshoes.

A peninsula on a peninsula that becomes an island at high tide.

At this site, two historic stone bridges spanning the Sing Sing Kill—one right on top of the other.

This bleach-white graveyard overlooking the ocean is accessed through a tunnel.

On a clear day, you can see all the way to the Virgin Islands from the top of this observation tower built in the 1960s.

A magnificent waterfall nestled in the heart of the El Yunque National Forest.

Everyone from Alan Ginsberg to The Rolling Stones has stopped by this classic dive bar.

This chapel on a cliff is renowned for its healing powers and was founded on the site of a supposed divine intervention.

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

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

The short hike is worth the stunning views and crystal blue waters of a secluded beach.

Puerto Rico's oldest rum producer started its 140-year-old business with "a little barrel."

Legend tells how a Spanish soldier disappeared from this isolated sentry box without a trace.

A park where people have been going to feed friendly pigeons since the 18th century

The world's brightest bioluminescent bay.

Look up from the busy streets to discover how time is kept!

This rowhouse doubles as one of the most photographed spots in the nation's capital.

One of Indiana's only natural sandstone arches is nestled between resort ruins and an old Boy Scouts camp.

Walk down these stairs to get an underwater view of Switzerland's Lake Zug.