Kastelskirken

Kastelskirken (the Citadel Church) is a historic garrison church dating back to 1704, originally built to serve the soldiers and officers of the Kastellet fortress. It's a quietly powerful place — one of Copenhagen's oldest active churches, tucked inside the star-shaped citadel that still functions as a military area. If you're walking the trail past The Little Mermaid and the Botanical Gardens, this is a genuine highlight worth slowing down for.