If you only have the chance to see one place in London, I think you have to visit Westminster Abbey. Westminster Abbey is one of the greatest examples of Medieval Architecture known to man. One of my favorite parts of the Abbey is the coronation chamber, where almost all of the English Monarchs were officially crowned, from Edward the Confessor of the Saxon line, to Elizabeth II Windsor. I also really enjoyed the tombs; where you can see so many of the great people throughout British history's final resting place. I also really enjoyed the Shrine, Chapels, Organ, Quire and Cloisters.