In 2006,Japan and the United States agreed to close Futenma and move its facilities to another Marine base with a heliport built on reclaimed land offshore.

VOA: standard.2009.11.11

All the land between the water on the left side and a long, long way has been reclaimed from the sea.

天水之间广袤的大地在你左边,公路在填海而形成的土地上无限延伸

耶鲁公开课 - 欧洲文明课程节选

It's because they reclaimed land.

因为他们围海造地

耶鲁公开课 - 欧洲文明课程节选