10. Heathrow Airport
Heathrow is a major international airport in Hillingdon, London, and is the busiest airport in the entire United Kingdom, as well as the busiest airport in Europe. If you fly into England, you will typically fly into London, and into Heathrow Airport.
The airport is enormous, and has a large variety of designer stores and nice restaurants, so even if you have a layover, you won’t have to worry about finding things to do.