Frederiksø and Christiansø are the only two inhabited islands in the Ertholmene archipelago. Frederiksø occupies an area of only four hectares. There are remnants of fortifications erected during the reign of King Christian V, who wanted to create a naval fortification on the Ertholmene islands. The turbulent history of Frederiksø and the entire archipelago is commemorated in a museum located in the most characteristic building on the island – Lille Tårn, i.e. Small Tower. The stone tower was erected in 1687 and exhibits, among others things, a collection of weapons.
