Valletta's coastal walk follows the rocks outside the city walls, giving a rougher and quieter view of the fortress city than the main streets above. Starting near the Sliema ferry, you can work around the peninsula toward the harbour side and climb back into the city near the Malta Experience.
Allow about half an hour if you keep moving, longer if you stop for the views. The route crosses bare rock in places, so it is best done in dry weather with proper shoes.