From our Sydney to Darwin plane (see Australia map).  Look at the global sweep of the sky above, and the brown Outback down below, which we never got any closer to than Katherine, the next couple of days after this.  The odd paradox about Australia is that it's a country with a far smaller population than the U.S.--about 1/18th our population while about the same size as our 48 states--so there's a lot more wilderness and open country, yet the population is even more urban than ours, for the simple reason that most folks live in the coastal cities rather than the desert Outback that fills most of the continent.  (Australia is the world's largest island and its smallest continent.)  Just four cities account for more than half of Australia's population:  Sydney (4 1/2 million), Melbourne (3 million), Brisbane (1 1/2 million), and Perth (1 million). 

By the way, this was the fourth of ten  plane rides we took on this trip:  PIT to Dallas, Dallas to LAX, LAX to Sydney, Sydney to Darwin, Darwin to Cairns with a stop enroute in little Gove, Cairns to Melbourne, Melbourne to Auckland, Auckland to LAX, LAX to Vegas, and Vegas back home to PIT.