History and specifics
Boats on the ocean approaching from the west would have to traverse a corner and not come into sight of the port until it was almost ready to dock.
Without the port at Yvrig, Natlar Port became the only viable port on the southern part of the continent, triggering a massive increase in traffic. This also caused it to become a target for the Lerrit Navy after their renewed aggression against the Perikia. When the conflict appeared to be going against the Lerrit, they set fire to the port in order to damage their enemy where it hurt the most as a final defiant act of a navy that knows it had lost. (DS9 - Gateways- What Lay Beyond short story: "Horn and Ivory")