Generally, cats are able to jump approximately six times their own body length and this can of course change depending on momentum, spring and surfaces that they are dealing with.
The question of whether it is safe to place fragile items high is subjective as they can become a target of interest at any point. Certain breeds will enjoy lounging in high places, gazing down at their surroundings while others will remain ground bound. Knowing a cat and understanding the risks involved in a surrounding is important.
