Umm...don't think the Beetle has one, unless something has changed in recent model years. You can buy this spiffy aftermarket one www.frostheater.com They make one for the diesel or for the gasoline. I'd put one in my 2.0 except I've changed the coolant about 3 times in the past 6 months (installed gauges - temp sender, replaced water pump, replaced coolant flange/thermostat) and I'm tired of doing it. It gets parked in a non-heated garage overnight anyway.
What they had in the past was an oil pan heater, a little sticker that they would put on the bottom of the oil pan, which would plug in and keep your oil warm. That was since discontinued and they have came out with an "In line heater" which they insert into one of the hoses (or something to keep it warm).
Last year I tried to get one and they were severly backordered, you might want to talk to your dealer about if they can get one for you.
By default VW's do not come with a block heater...
Right, I forgot about the in line block heater that VW is now offering. I priced it out last year and it was in the neighbourhood of $200 CDN, whereas the one from www.frostheater.com does the same thing for $60 US.