Madrid hop-on-hop-off ubus

Could anyone tell me if Madrid has a hop-on-off sightseeing bus - like the ones in London and New York? If so, where do you get tickets etc and roughly the cost.

many thanks

I've seen those buses in the Puerta del Sol. But can I get on my caja de jabon here? (!) Native New Yorkers HATE those buses, for good reasons (traffic snarlers, polluters, noise, etc). Madrid is VERY compact and you can walk to all the interesting places. The best "hop on bus" I know of is the regular old CIRCULAR (don't know the #)-- the bus that for about a dollar takes you all around the edge of the city. The same applies to the minibuses that go up and down the Castellana, from Atocha all the way to the "new" parts of Madrid. You'll be much happier exploring on your own, I think. rgf