City guide
London LHR: What to Do on a Layover
Borough Market in 3 hours: Tube to London Bridge, cheese toasties, back by gate.
Getting from the airport
LHR to city center: 44 minutes by rail (Heathrow Terminal 4 - Abbey Wood). Trains run every 3 minutes. Service runs 06:00 to 22:00. Skip the taxi unless your connection is under 5 hours.
What to do in London
The stops worth making: British Museum, Tower of London, Hyde Park, West End shows. Rated above 4.4: Buckingham Palace (4.5), The British Museum (4.7), Harrods (4.4), Big Ben (4.6), London Bridge (4.6). You do not need the full tourist circuit. Pick two and commit.
Visa and entry
London is visa-free for US passports. No application, no fee. The border process at LHR is efficient. Expect 15 minutes or less.
How long do you need
The minimum useful layover is 5 hours. That gives you 44 minutes in each direction plus about 122 minutes on the ground. Up to 72 hours is a proper overnight.
LHR airport
LHR has 22 lounges. For short connections under 4 hours, the terminal is the destination: food options, showers, and enough space to reset before the next leg.