This old cement mine has been used as everything from a mushroom farm to a recording studio.

This otherwise innocuous bodega was once the headquarters of the most feared assassin's guild in American history.

A ruined mansion hidden in the woods of the Hudson Valley, home of a tragically doomed romance.

A Manhattan courthouse hides a small but scathing memorial to Holocaust injustice.

A natural gas leak provides a flickering flame beneath a waterfall.

A masterpiece of LGBT art has been restored in what may now be the most valuable restroom in America.

This eccentrically decorated palace is replete with grottoes, fountains, tunnels, and caves.

The floating gallery illuminates the heart of Québec City's arts district.

This former prison now houses a lovely library devoted to Quebec's oft-maligned English-speaking history.

This lovely, if imposing, piece of Canadian gothic is possibly the most photographed hotel in the world.

This natural sea cave hides a small wonderland of natural turquoise beauty.

This Danish castle is supposedly haunted by a woman too independent to not be a witch.

The decaying remains of a 1960s mechanical wonderland that never officially closed.

This Denmark theme park is part family attraction, part experimental archaeology project.

A walkable map of the world, made from soil and stone by one man.

A wonderfully strange collection of 500+ stuffed frogs doing people things.

This indiscriminate collection of audio antiques is trying to preserve the history of the audio industry one vintage appliance at a time.

Canada's largest graveyard boasts a lot of noteworthy artifacts as well as its own computerized mapping service.

Designed by Buckminster Fuller, this relic of the 67 Expo survived fire and ice.

A carriage house converted into what resembles an 11th-century English manor house

A library of only unpublished manuscripts.

Some big-name visitors have patronized this small-town library named for an oil man's daughter.

A room hidden behind a swinging shelf in the children's section.

Possibly the smallest church in the world floats in the middle of a pond.