This is a must-do if you are in this area and trips are offered not only from Playa but also Ancun and Tulum. Organised tours usually put small groups into minibuses but do not befooled by the salesmen - groups to tour around the site are unlikely to be small and it takes more than two-and-a-half hours to get there because of the stop at a souvenir stall! Still, the ruins are big enough to disperse the hundreds of tourists pretty well and a good guide will reveal lots about the history of the ruins, which are probably the most well restored temples of all. On the way back most trips drop into a Cenote, a limestone sinkhole cave where you can swim (although with hundreds of tourists also feeding through here every day it can be a bit grimy!).
Playa del Carmen, Mexico
Adventure Tour, Ruin, Cultural Tour
Various tour agencies, US$45.