This is the oldest surviving purpose-built museum in the whole world don’t you know…
(And they have an alethiometer!)
This museum may not have the most fascinating title, but it is honestly one of the most interesting museums I’ve ever been in! First of all, it is steampunk heaven! Or Clockwork punk really, because there was actually very little in there that ran by steam, but an awful lot of clockwork items, plus early scientific experimental tools of the trade. The astrolabes, orreries, planispheres and armillaries I found hugely fascinating and look 
amazing. There was also a large section on Victorian medical instruments, early photography and telescopes. Lots of early devices to tell the time; instruments of map reading and navigation – all very clever indeed and much of it invented by Oxford scholars.
There was a family friendly Time Travel exhibition and trail for children while we were there, and they regularly hold talks and lectures. Well worth a visit – I’d definitely like to go back. And it’s free! (Donation box).
