Tim Dunn visits one of his favourite railway lines, the Ffestiniog in north Wales. Originally built in the 1830s to transport slate down the mountains to the coast, these days it's a tourist line – but it's filled with hidden architecture. Tim visits everything from the blacksmith's shop at the bottom where locos are still serviced to the line superintendent's house (with its own private platform) halfway up the line; he also inspects a tunnel portal up close and gets a guided tour of the famous spiral that lifted the track in the middle of the 20th century.Tim also finds out about Amsterdam Centraal which, in the 1880s, was controversially built right across the city's waterfront, ruining views of the sea. Three artificial islands were built to support the stunning neo-renaissance station building. But the then king refused to attend the grand opening. The royal waiting room still exists and we get special access behind its golden gates.Tim also looks at the opulent Landmark Hotel, built opposite Marylebone station for passengers of the Great Central Railway. The building's detail is exquisite and we get to see inside a secret tunnel below ground and find out about the cycling track on the roof!