Cobá's ruins include the tallest pyramid in Quintana Roo (the second tallest in all the Yucatán) and the thick jungle setting makes you feel like you’re in an Indiana Jones flick. Many of the ruins are yet to be excavated; for now they are mysterious piles of root- and vine-covered rubble.
If walking to the various sites is too taxing, you can rent a bike or hire a peditaxi.
