Palenque in Mexico, Tikal in Guatemala, and Copan in honduras are the 3 famous name that point out when talking about maya heritage. There are dozens of other sites, but those 3 are special.
Palenque was our first one, and I was amazed by it. tikal beats it though. Huge area of temples in the middle of the jungle. A day is a minimum to see everything. It is not only ruins, but also flora and fauna associated to the jungle. We saw animals jumping or flying from trees to tress, such as different kinds of monkeys, toucans, and some wierd mammals i cant remember the name of.
we visited in the evening after 3 and our ticket was valid for the day after. we took a guided tour that started at 4.45am (¡) to see the sunrise from the top of temple IV. Then the guide took us around the various places. He was exceptional.
Those first pictures may look too dark on your screen, but they actually do show features as the sun comes out.