The so-called Powder Tower (Kruttornet) is the oldest monument in Visby. It was built in the 12th century to protect the harbour. There was initially no door in the tower, but only a small entrance in 10 meters high. Defenders used ladders to climb up to the entrance. Today 25 meter high tower is open to the public in summer season.
References:La Hougue Bie is a Neolithic ritual site which was in use around 3500 BC. Hougue is a Jèrriais/Norman language word meaning a \'mound\' and comes from the Old Norse word haugr. The site consists of 18.6m long passage chamber covered by a 12.2m high mound. The site was first excavated in 1925 by the Société Jersiaise. Fragments of twenty vase supports were found along with the scattered remains of at least eight individuals. Gravegoods, mostly pottery, were also present. At some time in the past, the site had evidently been entered and ransacked.
In Western Europe, it is one of the largest and best preserved passage graves and the most impressive and best preserved monument of Armorican Passage Grave group. Although they are termed \'passage graves\', they were ceremonial sites, whose function was more similar to churches or cathedrals, where burials were incidental.