A pole of inaccessibility with respect to a geographical criterion of inaccessibility marks a location that is the most challenging to reach according to that criterion. Often it refers to the most distant point from the coastline, implying a maximum degree of continentality or oceanity. In these cases, a pole of inaccessibility can be defined as the center of the largest circle that can be drawn within an area of interest without encountering a coast.
Wikipedia – Pole of Inaccessibility
Continental Pole of Inaccessibility
On land, the point furthest (about 2,510 km) from any coastline lies somewhere near the Dzungarian Gate, a mountain pass on the border between China’s Xinjiang province and Kazakhstan: “the one and only gateway in the mountain-wall which stretches from Manchuria to Afghanistan, over a distance of three thousand miles [4,800 km].”
They say it might even be the home of Boreas.
Oceanic Pole of Inaccessibility (Point Nemo)
In the oceans, the point furthest [about 2,688 km] from any land lies in the Southern Pacific Ocean:
[at] roughly 48°52.6′S 123°23.6′W… It represents the solution to the “longest swim” problem. This problem poses that there is one place in an ocean on earth where, if a person fell overboard while on a ship at sea, they would be at a point that is the longest distance to any land in any direction.
…
The area is so remote that—as with any location more than 400 km (250 mi) from an inhabited area—sometimes the closest human beings are astronauts aboard the International Space Station when it passes overhead.
Wikipedia too – Pole of Inaccessibility
They say it might even be the home of Cthulhu.
Further out and deeper in
It doesn’t sound like Point Nemo has much to recommend it, but every continent and ocean has its own pole of (geographic) inaccessibility too.
And there are other types of inaccessibility. What places / ideas / feelings / results are difficult to access but worth your time and effort?
Ideas in a bottle please.