Sonderborg Castle

A castle has stood on this point above the Als sound since the twelfth century, guarding the crossing, and the building was remodelled repeatedly, most substantially in the 1720s when it was rebuilt as a baroque palace in yellow render around a courtyard, which is broadly what stands today. Christian II was held here for seventeen years in the sixteenth century. The chapel of 1568 survives as one of the earliest purpose-built Protestant church interiors in the world, largely unaltered, with its original fittings and gallery. The castle now houses the museum of southern Jutland, covering the region's long and complicated history, its shifting frontier, and daily life on Als, with the sound and the bridges visible from the windows.

What you actually see

• The 1568 chapel - among the earliest surviving purpose-built Protestant interiors.
• The baroque courtyard block - the 1720s rebuild in yellow render.
• The regional museum - southern Jutland's history across many rooms.
• The Als sound - the crossing the castle was built to control.

When to go

April to October for full opening; winter hours are reduced. Two to three hours. Weekday mornings are quiet. The waterfront outside is a good walk in any season.

Honest expectations

The museum is large and largely regional, with much of the labelling in Danish and German rather than English. The castle has been rebuilt so often that little medieval fabric shows. Winter opening is limited.

Nearby

Grasten Palace is west on the mainland; the Als coast runs north.