Carnival calls it the Sierra Madre tour. We personally didn't care for it but it was far to hot the day we went and the a/c on the bus was only marginal. We also ended up sick from the food at the restaurant you stop at for lunch. So you might want to bring some pepto along just in case. Also bring along plenty of bottled water if you are going during the hot time. It is an all day tour ending up with an hour to shop at the Golden Zone before they take you back to the ship.
I also do this tour in a private van with air conditioning if you are interested. I have been a licensed tour guide for 20 years. The sierra madre is a longer tour then the colonial tour. If you would like me to tell you exactly about the stops contact me and I will gladly give you this information.