1) The Stockton & Darlington (First in the World)
2) Mallard (Fastest Steamer Ever)
3) Channel Tunnel (Most amazing modern construction project)
4) Brunels original GW main line Paddington-Bristol (most original and far-sighted early construction project)
5) The original Japanese bullet train (makes the HST look like a Hornby has-been)
6) Construction/joining of the East-West continental lines in the USA (for the speed of construction and administrative organisation alone). Everyone interested in railways should read the history of this construction project: it makes anything built in Britain look like a kid playing in a sandpit!
7) The Settle & Carlisle line (the line with the most romance, soul and scenery in Britain. And another staggering construction story)
took the words right out of my keyboard !