Thunder City was located at the edge of the Strait of Thunder. The city wall was only a few kilometers away from the beach. It could be said that Thunder City was a naturally exquisite outpost fortress.
If the people from the Roland Continent intended to disembark on the Radiant Continent, the most appropriate place would be at the northern coastline outside Thunder City.
Perhaps God, in the creation of the world, deliberately gave the Radiant Continent a fine terrain. The coastline of the Radiant Continent at the Strait of Thunder had a lot of whirlpools, reefs and steep cliffs. There were very few beaches. There were even fewer places for landing a big military force. But there is one exception. Thunder City's beach front is flat and large, a perfect landing spot.