Kalmar Castle is a historic fortress located in Kalmar, Sweden. Built in the late 12th century, it served as a royal residence and a military stronghold. The castle played a significant role in the defense of Sweden and was a key site during the Kalmar Union, which united the crowns of Denmark, Norway, and Sweden. The castle features a mix of architectural styles, reflecting its long history. Visitors can explore its well-preserved rooms, including the grand halls and the chapel. Today, Kalmar Castle is a popular tourist attraction, offering guided tours and exhibitions about its rich heritage.