London is an arcology on Earth. Upon the original traditional city settled in pre-historical times, through Celtic, Roman, English and British eras, protective domes were erected in the 21st century to defend it from Earth’s wrecked environment.
As of 2070, the Central-North Dome was completed and others were planned or already under construction (SE):
(Note: This list consists only of items mentioned in the sources. It may be very incomplete.)