London is 5100&#x2F;sqkm, with 7.125 billion people, you&#x27;d need 1,397,059 sqkm, or 539,407 sq. miles.<p>Texas is 268,820 sq. miles. You&#x27;d need higher density than Manhattan to fit all these people and have any hope of growth.<p>Supplying such a monster would be a logistical miracle (or nightmare, depending on your perspective). Water alone would be extremely challenging - where are you going to get a steady supply and where can you store it?