Ancient Greek architects employed several illusory techniques to enhance their works. One of the most widely used techniques was 'entasis', the addition of convex curves to the columns of temples. The most famous example of entasis is the Parthenon of Athens, where the columns lean inwards as they rise, in theory converging one mile into the sky if allowed to continue. One of the biggest questions, however, is why this was done at all. Some suggest it was an aesthetic choice - at the Parthenon, the entasis gives the effect of swelling, as if burdened by the weight of the building's roof. Others believe it was to increase the impression of straight columns when standing outside looking up. This is because the Parthenon doesn't have any straight lines - simply the illusion of them.
