A water reservoir disguised as a castle stands atop a hill in a park in Stockholm city.

There are hidden patterns on the subway seats of some Stockholm metro cars.

This pair of unsuspecting buildings are in fact the very first modern skyscrapers in Europe.

This innocuous-looking button may have been used to assassinate a king.

Celebrating the Swedish ship used in the first Arctic expedition to navigate through the Northeast Passage.

One of the world's first dedicated bank buildings in the world is now the oldest one.

A competition inspired by Stephen King's psychological horror novel "The Long Walk."

This statue and park honor the Swedish chemist Jacob Berzelius, one of the founders of modern chemistry.

A large collection of ancient runestones decorates this university courtyard.

A heated statue pays tribute to one of Sweden's great actresses.

A prehistoric geological oddity tucked behind Stockholm's natural history museum.

Legend says this fabled well held part of a mythical Norse tree.

A concrete mushroom that divided Stockholm residents for nearly a century.

A traveling Bronze Age sacrificial stone that was used to honor elves, fairies, and other woodland spirits.

The world's biggest version of the popular Swedish souvenir.

The official meeting point for the oddly named governing assembly of ancient Sweden.

Several cannonballs of mysterious origins decorate two buildings in Stortoget's main square.

This mysterious runestone embedded in a church wall is linked to the medieval cult of Saint Erik.

A nightly tradition fills the streets of Flogsta with a collective scream.

Ancient burial grounds of the wealthy.

Inside this church, a monument honors the first burial site of the famed philosopher.

A temporary art piece to celebrate LGBTQ Pride is now a permanent part of Stockholm's traffic landscape.

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

A golden plaque marks the site of the mysterious unsolved assassination of the former Swedish prime minister.