EDSAC (the Electronic Delay Storage Automatic Calculator) was one of the world's first computers: it was built in the late 1940s, using electronic valves instead of not-yet-invented transistors. Unfortunately, it wasn't preserved, so a team of volunteers is now building a replica, to be used as an exhibit at the UK National Museum of Computing. It's a big job: it contains about 3,000 valves, mounted on 140 chassis, and each chassis takes at least 20 hours to wire up.
More details, for those interested, in the inevitable
BBC article.
