Normally used as a picture of secludedness and absence of communication, as in "academics doing their own thing in their ivory tower".
See this link: http://www.quinion.com/words/qa/qa-ivo1.htm
I don't have an IvoryTower. I just have a sanctum sanctorum from which I dispense good code (and posts).
You need to get out of your IvoryTower.
How many elephants would you need to kill in order to construct a complete tower of ivory?
Is that a standard-size or a double-height tower?
African or Asian Elephants?
I always thought that an ivory tower would be a normal tower covered in ivory panelling, rather than a tower made entirely of ivory.
See also TheBlackTower, TheoreticalRigorCantReplaceEmpiricalRigor