The impressive ruins of Hammershus Slot, dramatically perched on top of a cliff 74m above the sea, are the largest in Scandinavia. The castle was thought to have been built in the early 1300s, and a walk through the evocative site, enjoying the views, is a must for Bornholm visitors. The grounds are always open and admission is free. A smart new visitor centre is being built, sympathetic to the surrounds (opening 2018; likely with an admission fee for exhibits).

　　Construction of the castle probably began around 1250 under the archbishop of Lund, who wanted a fortress to protect his diocese against the Crown, engaged at the time in a power struggle with the Church. In the centuries that followed, the castle was enlarged, with the upper levels of the square tower added on during the mid-16th century.

　　Eventually, improvements in naval artillery left the fortress walls vulnerable to attack and in 1645 the castle temporarily fell to Swedish troops after a brief bombardment. Hammershus served as both military garrison and prison – King Christian IV’s daughter, Leonora Christina, was imprisoned here on treason charges from 1660 to 1661.

　　In 1743 the Danish military abandoned Hammershus and many of the stones were carried away to be used as building materials elsewhere. Still, there’s much to see.

　　There’s an hourly bus (2 and 8) from Sandvig to Hammershus, but the most enjoyable access is via footpaths through the hills of Hammeren – a wonderful hour’s hike. The well-trodden trail begins by the Sandvig Familie camping ground and the route is signposted.

　　If you’re coming from Rønne, take (infrequent) bus 7.