Crossing the line

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Across
  1. 3. Imaginary line separating governing entities
  2. 4. Set of beliefs, practices, and traditions of a group of people
  3. 5. Division based on human characteristics or behaviors
  4. 6. Elevated natural formations on Earth's surface
Down
  1. 1. Natural or man-made characteristic of the landscape
  2. 2. Boundary defined using straight lines or arcs