More specifically paintings from classical times always look flat or projected onto a flat area. Are there any ancient landscape paintings that show perspective? What about other non-european cultures? Did they have more advanced painting techniques before europe's famous renaissance painters?
a popular question! check out this section of the FAQ* for previous discussions - there are at least a couple of threads that focus on the development of perspective
Why wasn't ancient art realistic?
*see the popular questions link on the sidebar or the wiki tab above