In the northern part of the Swedish island of Gotland limestone has been quarried for building purposes and for burning into lime since the middle ages, and for many centuries lime was exported to ports in mainland Sweden, Denmark and Germany. The demand for limestone was particularly high around 1900 when large quantities were sent for use as a flux in blast furnaces in Germany and elsewhere. At that time there were about 30 quarries in the northern part of Gotland, all worked entirely with hand tools. During the twentieth century mechanisation increased, and a substantial proportion of the limestone quarried was used to make Portland cement. Lime burning in the Blasé area near the town of Läbro ceased in 1946 but limestone extraction from the quarries continued until 1956. The large-scale working of limestone continues elsewhere on Gotland. The lime works at Blasé was donated to a charitable trust in 1983 and it was opened as a museum two years later, under the patronage of cement companies and tourist bodies. The brick buildings stand on the shore of the Baltic and are dominated by two conical kilns.