Sir Christopher WREN was the Architect of St. Paul's Cathedral in London, England. He was an English scientist, astronomer, and mathematician who is best known for his work as an architect in the late 17th century. WREN designed and built many churches and other buildings in London, including St. Paul's Cathedral, which is considered to be one of the most significant works of English Baroque architecture. WREN's architectural style was influential in the development of English architecture in the 18th century.