St. Paul's Cathedral.
Famously, designed by Sir Christopher Wren, this is the fifth cathedral to stand on this site. According to evidence unearthed in the Great Fire of London in 1666, there was previously a Roman Temple dedicated to Diana.
The dome is two domes, one inside the other. The cross on the top is 365 ft above ground level. The first service was held here in 1697. Wren was interred here and, in 1924 the Architectural League of New York placed a new memorial to Wren, as a tribute to his "inspiration and enduring influence on American architecture."