High atop the Eiffel Tower is a small apartment built exclusively to entertain the science elite and make the rest of Paris jealous.

Abandoned railway line circling the city of Paris.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

This massive library holds what was once the largest book collection in the world.

Notorious artist squat renovated into legal studios.

A miniature model of the iconic Stockholm department store.

Sweden's oldest animated sign is still lighting up the skyline today.

Stockholm's deepest subway station is also a stunning ecological wonder.

The internet as provided by a James Bond villain.

The library's graceful rotunda is like a bibliophile's temple.

Sweden's first nuclear reactor, R1, can be visited 25 meters underground.

Stockholm's decidedly unique public transit system has doubled as the world's longest art gallery for decades.

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

The ruins of an abbey believed to have been founded by Charlemagne in the 9th century.

The first Russian Orthodox church in the Catholic city of Rome in almost a thousand years.

A modern sliver of architecture in Roma.

An abandoned Roman salami factory has found new life as an art space home to 200 squatters.

The studio built by fascists in the hopes of "reviving the film industry" with the occasional propaganda film opportunity thrown in.

A beautifully eclectic mix of architectural styles.

For one day every month Barcelona's Estació de França transforms into a market for model trains.

A once-secret library of Freemason history in Catalonia.

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

A temple to modernity, tucked away amid Barcelona's more well known museums.

A stately palace has been converted into the world's largest cannabis museum.