I used to have a great little 2mm N gauge layout of 'Watlington Station' I built when I was about 12/13,got broken up when I moved out and my old lady died though
My uncle has been building a live steam Black5 on and off for the last 20 years or so, its about 4 foot long!!! The boiler for it cost him nearly a grand!
Might have to buy my little un a train set now!