The red brick citadel of Stockholm's air defense

Kastellet stands on the islet of Kastellholmen. While it remains a constant in the Stockholm skyline, the current building emerged from a definitive catastrophe. The site originally housed a fortification designed by Erik Dahlbergh in 1667. That structure fell into disrepair after the Swedish fleet moved to Karlskrona in 1680.

In June 1845, an explosion occurred on the site. This event cleared the path for the current structure designed by Fredrik Blom between 1846 and 1848. He utilized red brick and designed a prominent round tower with a 20 meter high stair tower.

Despite its 19th century origins, the castle remained functional for modern warfare. It joined Stockholm's permanent air defense during World War II. During this time, the tower and battery plane were equipped with fast firing anti aircraft guns. The Swedish Coastal Artillery training school later used the site until 1990.

Today, the site maintains a specific and quiet duty. The Military Ensign of Sweden is hoisted and lowered every day from the top of the tower. This action signals that the nation is at peace.

Sources: Wikipedia, OpenStreetMap, Wikidata, Wikimedia Commons