We started our tour at Fort St Vincent near the town of Torres Vedras. It was major fort that has been largely preserved in the front of of the two lines near the western end. From there to the Atlantic the forward line was mainly a river line with dams flodding the valley. This fort has a small interp centre. For 1 euro (seniors discount) you get a short movie of re-enactors with the historical background, a small display & a map of the sites for self driving tour. The maps shows the forts that have survived but was woefully inadequate as far as helping one find them. If Ms Google didn't recognise the fort's name you had to be extremely lucky to find a signpost to it.