Well I'll ask my Prague colleague who's in our London office atm.
He mentionned a 50km+ trail that goes by several pubs, just outside the city.
The "trail" is not exactly in Prague, but starts from the town of Nova Pec (southern Bohemia), near the Austrian border. It's by a lake and is very "picturesque" with (little) mountains nearby.
More interestingly, it's got 17km of newly-laid tarmac, all flat. But beyond the new stuff lies about 100km of skateable paths... hmmmm... (and at 50p a pint of beer, that's a skating trip waiting to happen methinks).