Located a 2-1/2 hour drive to the west of Cancun is the world famous Chichen Itza pyramid built by the Mayans in 435 AD. This picture makes an excellent background for your desktop. Download a high resolution version (1024x768) here (do not use it for commercial use - you have my personal permission to use it for your desktop).
The steps on the pyramid are truly very steep. I took the picture to the left about half way up.
If you are a tourist you can book a discounted trip to see Chichen Itza here