The redeveloped waterfront, running for about a kilometre along the Als Strait from the castle north past the town centre, is where Sønderborg comes alive on a summer evening. Cafes spill onto the boards, sailing boats tie up at the inner harbour, and the wave-shaped multi-storey complex at the north end gives the skyline a single piece of modern drama.
Architect Frank Gehry's masterplan for the harbour, drawn up in the 2000s, is what gave the area its current shape. Not all of it has been built; what is there mixes residential blocks, restaurants and a small marina.