I'd go for a week in the winter. I'd love to visit Big Ben, Parliament, Westminster Abbey and Buckingham Palace. I'd like to ride on a double-decker bus and go shopping in the fashion district and also visit all the old castles!
Westminster Abbey is one of the quintessential visions of London, and one of the most impressive places to get to know the kings & queens of old. The Collegiate Church of St Peter at Westminster, London - "Westminster Abbey" at night.