Desert

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Across
  1. 3. In millions, like dust
  2. 4. Three times 'warm'
  3. 9. Your'e lucky if you find one
  4. 11. When you are by yourself
  5. 12. The wanderers of the desert
  6. 13. Flora and ..
  7. 15. A group of No2
  8. 17. Drops from the sky
  9. 18. .. Grylls. Also the name of an animal.
  10. 19. Ancient civilization of pharaohs
  11. 20. It doesn't need water to survive
Down
  1. 1. They sting
  2. 2. They crawl
  3. 5. They look like hills
  4. 6. No18 built them
  5. 7. Stay hydrated!
  6. 8. Has two humps and walking
  7. 10. The most famous one
  8. 14. They grow there
  9. 16. Famous city in there