This elaborate tunnel is the first structure composed of cast concrete in the United States.

This striking arch, one of the first architectural elements constructed in Prospect Park, was recently restored to its original glory.

A large boulder marks the place where the island of Manhattan was purportedly "sold" to the Dutch.

The highest point on the island known for buildings that touch the sky.

This miniature village stays behind in the Breuer Building, even as the museums around it come and go.

In the Compton Hill Reservoir Park sits a statue whose lack of clothing caused a scandal for the group that commissioned it.

Hundreds of graffiti artists have decorated this flood-wall on the west bank of the Mississippi River.

A strangely angled West Village home is the only monument to an explosion that took the lives of three American revolutionaries.

An aptly-named street near the birthplace of the modern LGBT rights movement.

This mausoleum is the final resting place of one of St. Louis's richest and most tragic families.

The first rural cemetery west of the Mississippi is home to the elaborate tombs of St. Louis' local beer barons.

One man's unrequited love stands in a glass box forever.

This unassuming riverbank is Missouri’s first designated site in the National Underground Railroad Network to Freedom.

A living memorial to the trees London lost during the Great Storm of 1987.

This Underground station has been a popular filming location for decades, even before it closed.

The handiwork of a underdog clockmaker who solved an impossible problem for an Empire, and forever revolutionized seafaring.

This ancient oak plays host to carvings of magical elves, gnomes, witches, and other creatures prominent in local folklore.

Dictionary Johnson’s favorite feline.

A charming 17th-century alley is lined with secondhand bookstores and antiquarian shops.

This massive collection of British military artifacts includes the heartbreaking personal letters of the men in the trenches of WWI.

The bridge is a secret gallery of discarded gum that has been transformed into miniature masterpieces.

A sculpture outside London's oldest cathedral honors the Mohegan chief who died while petitioning the king.

Originally meant to hold a statue of King William IV, this support sat empty for years. Today, it hosts a rotating cast of public artwork.

These official units of measurement—including chains and perches—lie hidden beneath tourists' feet in a popular London hub.