See COVE Master Map entry on Istanbul: 

https://editions.covecollective.org/place/istanbul-0

In London Labour and the London Poor edition: 

Phase 1

London Considered as a Great World. (The Great World of London) [as Constantinople]: "In short, London may be safely asserted to be the most densely-populated city in all the world - containing one-fourth more people than Pekin, and two-thirds more than Paris; more than twice as many as Constantinople; four times as many as St. Petersburg; five times as many as Vienna, or New York, or Madrid; nearly seven times as many as Berlin eight times as many as Amsterdam; nine times as many as Rome ; fifteen times as many as Copenhagen; and seventeen times as many as Stockholm."