Haapsalu's main sights cluster around the old town: the medieval castle, the wooden promenade, and the grand railway station. The compact centre is easily walkable — you can cover the highlights in a long morning and still have time for a mud bath in the afternoon.
The seaside aspect of the town becomes clear once you reach the waterfront. The gulf here is exceptionally shallow and warm, protected by a ring of islands, which is why Haapsalu attracted the nineteenth-century health tourists in the first place. The wooden Kuursaal pavilion on the promenade is the most photogenic spot in town.