London Heathrow Terminal 5 is a massive, high-tech structure consisting of eight floors (storeys) in total. The main terminal building (T5A) has five floors above ground and three floors below ground. The five above-ground levels handle the primary passenger flow: Level 1 is for arrivals and baggage reclaim, while the top levels (Levels 4 and 5) house the vast departures hall, check-in desks, and premium lounges. The three sub-surface levels contain the infrastructure for the Heathrow Express and Piccadilly Line underground stations, as well as the sophisticated automated baggage handling tunnels. The terminal is designed as a "toast rack" layout, with the main building connected to two satellite terminals (T5B and T5C) via an underground transit system. The sheer verticality of the building—the largest free-standing structure in the UK—allows it to process over 30 million passengers per year while keeping the footprint relatively compact between the airport's runways.