When architect Sir Christopher Wren designed the interior of Windsor Town Hall near London in 1689, he built a ceiling supported by pillars. After city fathers had inspected the finished building, they decided the ceiling would not stay up and ordered Wren to put in some more pillars.
Englands greatest architect didnt think the ceiling needed any more support, so he pulled a fast one. He added four pillars that did not do anything -- they dont even reach the ceiling. The optical illusion fooled the municipal authorities, and today the four sham pillars amuse many a tourist.