So, I just came back from a couple of weeks of beautiful weather in Mexico City. I became a little obsessed using 123D Catch at different locations, and am slowly working through them. The additional practice in taking the pictures and submitting them to the cloud service has been useful to help me understand better ways of creating these models from pictures. My biggest tip if you are starting is to take pictures as you move around the object.
Here is the Piedra del Sol at the Museo de Antropología, also known as the Aztec Calendar resulting from 10 pictures taken with my Android phone. I will post a few more examples of the architectural tests I performed while on a tour bus.