The Fortification Glazed by 1,100 Degree Furnaces

The stones of Broborg underwent a profound transformation into glass. Scientific analysis of the inner rampart confirms that the rock was subjected to temperatures surpassing 1,100 degrees. We can conclude that the builders utilized enclosed furnaces and bellows to concentrate heat within a restricted area. This process created a permanent glaze over the fortification. We must now investigate the specific motives behind this deliberate modification.

This defensive structure occupies a high ridge near Stenby gård. It overlooks the historic maritime path connecting Uppsala and the sea. The site spans approximately 95 by 85 metres. It consists of a ring wall, double ramparts, and two entrances. Investigations conducted in 1982 uncovered house foundations. Carbon dating from a post hole dates to a period matching a found glass bead. The construction incorporates charcoal, granitic gneiss, and amphibolite.

We can still see the remains of the ruins and a circular stone structure today. A triple spring flows to the northeast. According to local legend, the chieftain's daughter Grimsa lived in the fortress. Her brother and his men attacked, and when Grimsa realized the battle was lost, she set fire to the supply houses and sacrificed the entire facility. The resulting flames were said to be visible as far away as Gamla Uppsala. Grimsa died of intense weeping, and her brother subsequently burned her body. A burial mound near the fortress has been called Grimsahögen since at least the 1500s.

Sources: Wikipedia, OpenStreetMap, Wikidata, Wikimedia Commons