One of the most photographed buildings in a city known for its Modernista architecture is an abandoned squat.

This home designed for chocolate magnate Antoni Amatller is an exquisite treasure-box of Catalan Modernism.

One of Antoni Gaudí's least-visited works, an homage to Catalan patrimony that mixes neo-Gothic with Modernista forms.

This cafe offers a curated collection of treats and tipples made by monks and nuns.

A collection of trees from various corners of the world call Stockholm University home.

Despite dreams of constructing this fairytale mansion, Albert Gotthard Nestor Cedergren never saw its completion.

The apartment where Pippi Longstocking came to life.

This railroad track was so secretive that it was omitted from all maps.

A 12th-century church with a medieval fresco and an intriguing “Greek runestone.”

Sweden's "good old days" painstakingly re-created in a model village.

It houses the remains of a 17th-century version of the Titanic.

A hidden bathhouse in one of Stockholm's oldest and busiest neighborhoods is open to anyone who can find it.

This titanic Catholic church in Chicago is also a refuge of the fictional cult-favorite wizard detective Harry Dresden.

First planned industrial community in the United States.

A gothic church spire sits atop this skyscraper, the tallest church in the world.

A haunting statue called "Eternal Silence" has quite the reputation among visitors with active imaginations.

An enormous park-like oasis, full of famous Chicagoans' graves.

A lush green oasis in the middle of Chicago.

The house where the famed outlaw was shot by a dirty coward is now a museum to the criminal's legacy.

This secluded aqua waterfall in the Grand Canyon is the perfect swimming hole, and the Havasupai tribe's fiercely protected natural wonder.

Ancestral Puebloan ruins, natural arches, and box canyons abound in this seldom-visited corner of Monument Valley Navajo Tribal Park.

Rippling sand dunes frozen in the Arizona rock.

The hike through a narrow river flanked by the 2,000-foot-tall walls of Zion Canyon is one of the best in the world.

The largest island on the great salt lake is home to curious creatures and strange stories.