Austin’s nonprofit-run graffiti park where street art is meant to be painted over.

Home to the largest urban bat colony in North America, estimated at 1.5 million bats.

Thanks to an acoustic anomaly, this unassuming stone bench has heard one hundred years of secrets.

"Holy Wisdom" overlooks the city that became its namesake.

Sofia's legislative center is continuously reinventing itself.

A vast Communist-era exhibition space in the Bulgarian capital.

A striking symbol of the Bulgarian capital.

Eastern Bloc nostalgia, anybody?

An ancient necropolis of magnificent tombs.

A bust of Franz Kafka spins in pieces, reflecting the writer's inner torment.

A gorge full of caverns where early humans lived alongside cave hyenas, giant mammoths and wooly rhinoceroses.

An small and easily overlooked archaeology museum chock full of Egyptian artifacts.

Displaced highlanders would take shelter from the wet Scottish climate under the large walled bridge at Glasgow Central Station.

A mysterious echo seems to defy the laws of acoustics.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

A program of Communist glamour in post-Stalin Poland is preserved in this colorful museum.

Infamous marsh filled with toxic waste, World War II-era London rubble, and dead mobsters galore.

A historic covered bridge is but one example of an oddly prevalent American urban legend.

These 20-foot sculptures will help guide you from the local train station to the local sculpture garden.

This Delaware River bridge is emblazoned with a catty slogan from a more prosperous time.

The origin of this mechanical boy was a mystery until he revealed his maker by writing it in perfect cursive.

A clone-tree in Washington Square Park sprung from seeds that went to the Moon and back.

This elaborate towering structure was once famed for its revolutionary height.

While this monument tile is shrouded in mystery it also marks the end of the longest ever human chain.