[renw0rp]

On the topic, the oldest original running computer[1] can be found in the UK in the National Museum of Computing based in Bletchley Park (where Alan Turing and many others worked breaking German cryptography). The museum requires a separate ticket from the "main" Bletchley Park museum. It's around 1h trip from London Euston. Well worth a visit! Among other items, they have a working "Bombe" replica

[1]https://en.m.wikipedia.org/wiki/Harwell_computer

[cjs_ac]

When I visited a couple of years ago, it was quietly clicking away, computing prime numbers.

[tengwar2]

Not sure if it's still the case, but when I visited, they handed you a button to single-step through the program. You actually get to operate it, at some level.