User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-6951062-20130312053730/@comment-4902593-20130312121930

Space isn't the same when it comes to supernatural places. What you say is true but the entrance to Tartarus can be summoned anywhere, if a god or powerful monster wishes to (Poseidon summons one in TLO to send Typhon down). It is usually found in the Underworld. So basically if you want to access the Underworld, then you have to go to LA or the Doors of Orpheus in NYcity, but if someone wants to access Tartarus specifically, then they can access the entrance anywhere as long they are powerful enough to do it.