Stephen Wiltshire was diagnosed with autism at the age of 3.  He was mute and didn't relate with other people.  However, he is what is called an autistic savant.  It is like a deaf person can see sharper, or a blind person can hear things others can't.  Stephen is able to draw anything he sees, from memory, like the entire city of Rome.

His website has a large gallery of his work, and also some prints/originals for sale.  Some one needs to teach him how to pixel.