The mining of limestone was begun in Gotland in early Middle Ages. There was a significant lime kiln in Barläst, which was used to produce quicklime through the calcination of limestone. The kiln was used between 1690-1907. Today the area is a well-preserved sample of early industrial milieu. There are ruins of three lime kilns, the oldest one dating from the 17th century.
References:The Walls of Constantinople are a series of defensive stone walls that have surrounded and protected the city of Constantinople (today Istanbul) since its founding as the new capital of the Roman Empire by Constantine the Great. With numerous additions and modifications during their history, they were the last great fortification system of antiquity, and one of the most complex and elaborate systems ever built. They were also the largest and strongest fortification in both the ancient and medieval world.
Initially built by Constantine the Great, the walls surrounded the new city on all sides, protecting it against attack from both sea and land. As the city grew, the famous double line of the Theodosian Walls was built in the 5th century. Although the other sections of the walls were less elaborate, they were, when well-manned, almost impregnable for any medieval besieger.