Chichen Itza was one of the largest and possibly the most famous Mayan cities. It contains many fine stone buildings in various states of preservation, including the largest ball court in the Americans, a large Cenote (sacred well), largest observatory and iconic Chac-Mool alter overlooking a large pyrimid. Unlike other Mayan sites open to the tourists, none of the structures at Chichen Itza can be climbed or entered.
Read more on the (Wiki link) and view the site map here and another here.
Group photo at Chichen Itza
El Castillo
The Platform of Eagles and Jaguars
Platform of the Skulls (Tzompantli)
The Jaguar Temple and the largest Ball court in Mesoamerica
Tomb of the Chac-Mool
The Sacred Cenote (well of sacrifice) with its sacrificial Alter
Temple of the Warriors in The Group of a Thousand Columns
Temple of the large tables
Temple of Xtoloc located beside a second Cenote

Tomb of the High Priest

The Platform of Venus...

...with round platform
These were all located together and can be found on the map under Tomb of the High Priest

The Observatory

Another smaller Ball Court

The Church

the Nunnery
The Red House