Bull Island shouldn't exist. The granite walls thrown out from Clontarf in the 1820s to scour Dublin's shipping channel did their job — and then quietly silted up a sandbar into a three-mile island of dunes, beach and salt marsh, now a UNESCO biosphere on the city's doorstep. An afternoon walk out and back over a wooden bridge, with the geese, the long sand and the view to Howth.
Start on the Clontarf seafront and cross the Bull Bridge — a single-lane timber causeway that rattles under every wheel; walk it slowly. On the landward side, the lagoon and salt marsh fill with the tide and, in winter, with brent geese flown in from Arctic Canada. Over the dunes lies Dollymount Strand: five kilometres of sand, cars allowed at the south end, solitude if you walk north.
The dune spine carries a fenced bird sanctuary at its tip. Then out along the Bull Wall to the statue of Our Lady on her globe, for the view back at the city and Howth across the water. Recross the bridge at the turn of the tide and follow the seafront to the DART.