Sønderborg Castle is a historic fortress located in Sønderborg, Denmark. Originally built in the 12th century, it has served various purposes over the centuries, including as a royal residence and military stronghold. The castle features a mix of architectural styles, reflecting its long history and the different renovations it has undergone. Today, Sønderborg Castle houses a museum that showcases the region's history and culture. Visitors can explore its well-preserved rooms, exhibitions, and beautiful gardens, making it a popular destination for both locals and tourists interested in Danish heritage.