- Yields: Nothing
- Movement needed: blocks embarking/disembarking from this tile
Cliffs' main function is to present a defense against naval invasion. They usually come in "chains" - that is, in a series of nearby tiles - and you can use that fact to found a city which will be (almost) completely safe from naval invasions, since enemy land units will have great difficulty reaching it from the sea!
Note that a Harbor may still be built next to a cliff. When your units use it, they will be able to pass the Cliffs to Embark or Disembark. Enemy units won't, however.