[Yuri]

In the US, two groups, in no particular order inside them:

- New York, Chicago, Los Angeles, Philadelphia, Pittsburgh, Detroit;

- Cleveland, St. Louis, San Francisco, Atlanta


In the World:

- Hong Kong, Sydney, Johannesburg, London, Frankfurt, Cape Town, Rio de Janeiro, Toronto, Mexico City, Tokyo


I understand we're talking about skyline meaning skyscrapers and highrises. If it's to include any skyline, than I'd have several European cities.