Some time ago I read that Perth is the most remote city with more than 1 million people, 2100km away from the next city with more than 1 million people, which is Adelaide. Actually, this is wrong: according to this criterion, the most remote city in the world is Auckland.
This dataviz shows how remote some cities are. For each one of the 5 cities in this dataviz each dot represents another city with more than 50,000 people (a number arbitrarily chosen by the designer, a.k.a. me) at less than 100, 200 and 300km of it. Perth is, indeed, quite remote. Besides Perth I chose some famous cities and Floripa, the most beautiful city in the world!
Source of the data: Wolfram Alpha.