Ruins are an individual taste. One man's castle is another man's pile of rocks, sometimes not even a very impressive pile of rocks. Two friends of mine  (you know who you are) are great fun to accompany on a site visit. She sees a magnificent ancient greek temple, He sees a pile old rubble ripe for a unit development. Myself I have a bit of a foot in both camps. Mexico has many great Mayan/Aztec sites. Some of theses survived successfully for many hundreds of years, only to then be abandoned then resurrected by later civilizations. These people believed the original creators where gods. Teotihuacan,Chichen Itza, Palenque, and Monte Alban, are pretty much, must sees if you are going past. Thirty years ago I first visited  Mexico and wandered many of these sights. Tourist guides where the locals trying to make a buck, Fences and keep out signs were non existent. Pay ten Pesos at the gate or sneak in the back door. Bash your way through the bush like Indiana Jones and climb whatever you please. In the eighties for  twenty bucks I reckon I could have taken an excavator in with me. I have fond memories of sneaking up to the Sun Temple, climbing down and checking out  rocket man from "Chariots of the Gods" fame. Nothing like some Magic mushies and turning out the torch four stories down at midnight,in a burial crypt to bring history to life. Sadly such enlightened attitudes have changed. In Palenque a million peoples acid breath has closed the rocket god's tomb to visitors. Most of the major temples can only be viewed from the ground.The sites are still spectacular but a bit like Ayers rock It's not quite the same. Fortunately the ancients were productive little bastards.There still are plenty of lesser sites where you can climb till your heart's content. Unfortunately many of theses will fall into the pile of rocks category.

   Cenotes on the other hand are something I can never get enough of. The Aztec's believed in the heaven, the earth, and the underworld. Gods lived in heaven, temples on earth worshiped them, and foretold celestia events, Cenotes were the paths to the underworld, where virgins and captured enemies were sacrificed much to the relief of the goat population. Eighty million years ago a giant comet smashed into the earth just north of Mexico. The resulting shock waves shattered the limestone allowing water to seep in.  This eventually developed in to cave systems. Where the roofs collapsed in places, you are left with bright clear lakes connected with underground rivers, The water in them teams little fish, flickering shafts of light reflect off the walls. Stalagmites climb out of the warm pools,  underground rivers keep the pools crystal clear. Stick your head under the water and low roofed little caverns become grand ball rooms, full of mirror balls and mysterious paths to the unknown. These are the swimming pools you have always dreamed of having in your back yard. Maintenance free and ever changing.  Central America and the Caribbean are full of them. See Ya  later I'm off to catch up with the gods.