Which country does town 611 belong to?

In the absence of personally arriving at the destination, in order to open a "Teleportation Gate" to that location, determining the precise coordinates of the destination is a necessity.

As Reiger thought, sending a summoned creature ahead to reach the destination and then locating it through the mental connection between the caster and the summoned creature is one method, as is using intelligence magic such as "Message" to establish a position.

In the original work of the world of Overlord, Ainz once used a magical artifact known as a Distant View Mirror to confirm a teleportation location, thereafter moving there using "Teleportation Gate".

It was a magical artifact that could reflect the scenery of a designated place. After using that artifact to confirm the teleportation location's position, direction, and surrounding environment, Ainz teleported there using "Teleportation Gate".