The The Undercliff Walk is 4.5km long from the Marina to Saltdean. It is a white concrete walkway at the foot of the cliffs stretching from the Brighton Marina along the coast to Saltdean. The walk is open all year round, with breathtaking views of the sea on a clear day, or indeed a dramatic close up view of the waves on a stormy day. There are gaps in the cliffs at Ovingdean and Rottingdean where the Undercliff Walk can be reached by a set of steps.The Undercliff Walk was designed by borough engineer David Edwards, and opened in 1933. It was built as a solution to the damage that the sea was doing to the chalk cliffs through erosion. The Undercliff walk is maintained by the Council. The cliffs themselves are covered with wire mesh to protect walkers from falling flints. Many birds can be found nesting in the white cliffs, commonly gulls and pigeons.
http://www.thisbrighton.co.uk/cultureundercliff.htm (The website itself is no longer maintained, but there is still plenty of useful information about the Undercliff walk, and many pictures)