If it is only 2 nights you dont want to go too far.
For example if you live in Scotland it is no good us suggesting Cornwall.
It may help to tell us where you live.
The Hilton hotel do really good 2 night breaks which often include 1 nights dinner and breakfast both mornings.
These are often advertised in weekend papers like the Daily Mail or Telegraph (other hotel chains do them as well).
To be honest you can go to any city as there is ALWAYS something to do in or around any major city.
I have done Hilton deals and stayed in Stoke, Sheffield and Swindon (none of which sound that great) but have always found places to go and see.
Two great cities with lots of history are York and Chester.