Besides the wealth of prehistoric cultural sites, there are many more dating from other historic time periods--fortresses, castles, and manor houses from the Middle Ages through the 19th century. For example, Glimmingehus, in the far south of the country, is the best-preserved medieval fortress in Scandinavia. In the area around Lake Mälaren there are many fine examples of castles and stately homes dating back to the era when Sweden was a great power in the 17th and 18th centuries.