I've never found Peterborough to be a particularly interesting place. There's nothing really wrong with it, it's just seems 'dull' to me.
It's got a medium sized covered shopping centre which is little different to those anywhere else. Outside of the covered shopping, the city centre doesn't have a great deal to offer, except for a decent market (and, of course, the cathedral).
I've only ever visited Peterborough for day trips, so I can't report on the nightlife but it doesn't strike me as the sort of place which would exactly be 'throbbing' at night. I've always managed to find a decent meal, in a pub or wine bar, at lunchtime but it's not like some cities, which are packed with bars, restaurants and bistros. (Peterborough has no university, so it lacks the students who fuel the nightlife of many cities).
http://www.visitpeterborough.com/
If you're looking for a city which is attractive and full of history but packed with bars, restaurants, bistros and nightclubs, try Norwich:
http://www.visitnorwich.co.uk/
Ipswich also has a lot to offer (far more than Peterborough does) but it's not really as vibrant as Norwich:
http://www.visit-ipswich.com/
Chris