Sydney

Sydney is the most populous city in Australia.

History
When notorious international criminal Vanchat was arrested and succesfully interrogated by S.H.I.E.L.D., he revealed that one of the major purchases of Chitauri metal was located in a warehouse in Sydney.

Phil Coulson's team of agents, under orders of Agent Victoria Hand, flew to Sydney until new information about Coulson's location arose.

Trivia

 * Contrary to popular belief, Canberra, and not Sydney, is the capital city of Australia.