I've passed over the Ouse Valley Viaduct many, many times over the last 20 years on the train back and forward between London and Brighton. It's a beautiful view from the train windows - but what's under the trains is absolutely incredible.  A towering red brick viaduct standing at 29 metres high, spanning 450 metres, with 37 huge elongated semi-circle arches beneath. I've wanted to see it up close for a long time, so over the Easter weekend we took the train to Balcombe and walked down from there...