Sir Christopher Wren
Under normal circumstances, Sir Christopher Wren would probably be known as a great architect, but he might not have gone down in history as among the most famous architects that ever lived. As it happened, however, Wren was in the right place at the right time -- and he possessed the right talent.
Wren was a professor of astronomy at Oxford who came to architecture though his interest in physics and engineering. In the 1660s, he was commissioned to design the Sheldonian Theater at Oxford and visited Paris to study French and Italian baroque styles. In 1666, Wren had completed a design for the St. Paul's Cathedral dome. One week after it was accepted, however, the Great Fire of London raged through the city, destroying most of it -- including the cathedral.
The Great Fire created an unexpected opportunity for Wren, and he was soon at work on reconstruction. Although plans for a sweeping reconstruction of the city soon proved too difficult, by 1669, he was appointed surveyor of royal works, which put him in charge of government building projects. Ultimately, he had his hand in designing 51 churches, as well as St. Paul's Cathedral.