Christopher Wren (1632 – 1723), a great English architect, at the client's request, installed four additional columns in the Windsor Guildhall. The client's concern was that the roof was lacking structural support and was in danger of collapsing. Wren, who was not at all convinced that his design was structurally unsound, probably mumbled to himself something about the fact that the clients always ruin everything. Nevertheless, he built the four columns that apparently satisfied his critics.
The problem is, of course, that these columns do not reach the ceiling, and in fact support absolutely nothing. Upon very close examination, they turn out to be completely decorative! Hundreds of years later, the building still stands, complete with an architect's joke.