Introduction to Castellet Castle: Castellet Castle was once a fortification in Northern Europe. Now it has become a modern military base in Denmark. It has a five-pointed star shape and is very obvious on the map. Next door is the Little Mermaid statue, so this is the only place you must pass to reach the Little Mermaid, and it can also be regarded as a landmark building. Due to the military aspect, tourists can only visit and take photos in public areas, and must follow the icon instructions in the castle.