Let's say I'm building a world that is very much like Earth in almost all respects. It might have some small differences, but on the whole, it's essentially based on the real world.
Now, I'd like to place some element of this world in some location (in my mind it'd be on land, but if the answer allows for location on water in addition to on land, then only so much the better) that is a minimum, or perhaps exactly, a given distance away from a human population center with some specific minimum number (to a reasonable approximation) of people.
For example, if I want to place something 500 km from the nearest human settlement with at least 10,000 people, then likely 510 km from the central portions of Paris, France is likely not going to be a good choice.
Let's say I'm not very concerned about topography at all. If the solution can take topography into account, so much the better, but it definitely is not required.
I'm primarily interested in resources that are available online.
What resources are available for identifying at least approximate locations based on such criteria? How can they be used to identify such locations?