With the introduction of Mansions many people are being overwhelmed by the boulders they produce, therefor I am suggesting something to do with them.
It's basically a giant stone penis. You start the construction and it requires 1 stone and X boulders (however many boulders that would make sense for how big it is). Boulders are dumped straight into the building sign and don't have to be chipped to stones first. The finished construction will have a small number of hitpoints but would never be damaged by decay, so any that are built can be removed easily but would never go away unless someone removed it.
What do you think?