A little historical background on the Yucatan

Any history of the area must start with the Chicxulub crater which was discovered in the 1970's while drilling for oil in the Gulf of Mexico.  The impact of the Asteroid is credited with wiping out the dinosaurs.  Until Christopher Columbus happened upon a canoe of Mayan traders in 1502 no one gave much thought to the Maya except perhaps the other indigenous tribes that traded with them. When Hernandez de Cordova asked the 'Indians' the name of this land they told him "you speak to rapidly, we don't understand a damned thing you are saying" which he understood as Yucatan.  

Wikipedia is as good a place as any to start your study of  the Yucatan but no one should come without reading John Lloyd Stephens Incidents of Travel in the Yucatan  which chronicles his adventures with his side kick the illustrator Stephen Catherwood.  They are credited with rediscovering the Maya ruins in the 19th century.  What you're going to notice in Merida is the old historical center laid out in a grid like the Spanish cities laid out and built buy the Moors.  What's left from the Colonial period which technically ended in 1810 are mainly the churches. Most of the old houses were remodeled or destroyed.  The big beautiful casonas may date from the 16th to 18th century but the wealth of Merida in the 19th century put a Belle Epoque veneer on the old city.  There also seems to have been a big boom in the early 20th century and there are many art deco facades plastered on the old houses and of course some real deco treasures like the Teatro Merida on calle 62.

The cenotes theoretically date for the Asteroids impact and they are mostly scattered around the area from Merida to Valladolid ending at the Ruta Puuc hills.  The haciendas were first built on Maya sites using the stones from the ruins and these old haciendas are in line with the stars as were the pyramids.  The newer haciendas that were built in the 19th century with the henequen (sisal) fiber profits were grander and more fantastical structures.  Any vacation in the area should include a day or two exploring the cenotes, haciendas & ruins.  The current boom in renovation of the historic center of Merida began with a few Gringo's moving into the area to buy cheap real estate as seen here in this article from 1999 in the Wall Street Journal.  

photo of a gate at the Hacienda Yaxcopoil