There are a number of buildings that give +culture to a city: Broadcast Tower, the 7 religious "cathedral" sized buildings, and the Broadway, Hollywood, and Rock 'n Roll wonders each give +50%. The Hermitage gives +100%. In theory, if you managed to put all of these in one city, it would give you a +650% bonus to culture in that city. That Stonehenge would ramp itself all the way up to, um, 60 culture all by itself. Useful buildings, those.
I'm guessing that these bonuses are added to the individual buildings rather than the city as a whole, but I can't say that I've ever bothered to confirm this.