Complex sentence: Poldering Noord Beverland (the process the Dutch invented to reclaim land from the sea) didn't start again until 1598-the villages of Colijnsplaat and Kats were both built on estates at right angles to each other.
Split into simpler sentences: Poldering Noord Beverland (the process the Dutch invented to reclaim land from the sea) didn't start again until 1598. Then the villages of Colijnsplaat and Kats were both built on estates at right angles to each other.