[Varyon]

Another consideration is if it's possible to rapidly shut down the bottleneck - by damaging/destroying it, disconnecting it from its power source, physically blocking it (like the Iris system in Stargate), etc. Particularly if this shut down is readily reversible, this gives whoever controls the bottleneck a great deal of power over who can travel through it... and particularly if it's slow (or impossible) to bring back up, this can be the basis for attacks on it. In a case like that, with a two-way wormhole or similar, unless one side completely dominates the other, you'll require cooperation between the two for both sides to stay open. These can make them a decent option for the location of an embassy, or even an outright military base.