GeoGraph - photograph every grid square

Built in 1811 to seal off the Glaslyn estuary from Tremadog bay as a land reclamation measure, the Cob is a sea wall of 1.4km length connecting Porthmadog with the Penrhyn peninsula. Festiniog Railway [1] opened in 1836 to run gravity propelled slate trains from the quarries at Blaenau Ffestiniog to Porthmadog harbour, using the Cob to cross the estuary. There is enough space on the dam to carry a public footpath comfortably as well. The A487 road was added later on the landward side of the Cob and runs alongside the dam's inside wall for its whole length.
[1] (as the spelling was then)