Abereiddi to Porthgain and the Blue Lagoon

This is the walk to do if you only have an afternoon on the north coast.

Start at Abereiddi, where the beach is dark grey slate shingle and the cliffs behind are full of fossils. Follow the path north for five minutes to the Blue Lagoon — a slate quarry that was deliberately breached to let the sea in when the workings closed in 1910. The colour is real: it comes from the mineral content of the slate. It has hosted Red Bull's cliff diving series, and on most summer days there'll be a coasteering group in the water.

Above the lagoon are the ruins of the quarrymen's cottages and the tramway that ran the slate down to the harbour.

Carry on north along the cliff. The path is well made and the climbs are short. You pass Traeth Llyfn, a fine beach reached by a steel staircase, then round the headland into Porthgain.

Porthgain is the point of the walk. A harbour the size of a large garden, hemmed in by brick hoppers that once held crushed granite for road-building, with the quarry buildings still standing above. It was a working industrial port until 1931 and looks like almost nowhere else in Wales.

Where to finish. The Sloop Inn has been there since 1743 and is the obvious stop. The Shed, forty metres away, is a seafood bistro in the old machine shop. Both get busy — in August, eat early or late.

Getting back. Either retrace the path, which is no hardship, or use the Strumble Shuttle bus in season. There's no sensible inland shortcut.