St. Paul's Cathedral in London, England was designed by the renowned English architect Sir Christopher WREN. WREN, who is often referred to by his initials 'WREN', was a highly influential figure in the field of architecture and engineering during the late 17th and early 18th centuries. He is best known for his work on St. Paul's Cathedral, which was completed in 1710 and is considered one of the most iconic buildings in the world. WREN was knighted in 1673 and was later appointed Surveyor-General of the King's Works, a position he held until his death in 1723.