Kastellet fortress in Copenhagen
Alen Max/age fotostock
Her silhouette is used as a symbol for the city, and she is one of its most popular attractions, but there’s no avoiding the fact that the Little Mermaid is—as her name suggests—a very modest young lady. Many visitors are surprised by just how meek she seems, sitting on her rock in the harbor. To make the visit worthwhile, once you’ve seen her you should explore Kastellet (the Citadel). This well-preserved star-shaped fortress dates back to the 17th century and was once part of a ring of defenses that encircled the city. Troops still occupy Kastellet, raising and lowering the flag each day.