Any Possible way to build on Ancient Gates

So I am building a library that is next to an ancient gate and there was a ruin next to the library on the opposite side from the gate, I fixed it up and it looks nice, I had intentions to build some sort of tower or balcony from the library to the gate but the tower seems like a much better idea.
I did the measurements and the tower would have ended up on grass however the grass was indestructible and I could not build anywhere reasonably above it, the tower would only be 2 blocks off and the latitude of the tower can change within reason (0-20 blocksish) so if anyone has a way to build on the gate grounds or to move the gate I am willing to use mods, admin mode or whatever else, or I could move the whole thing down a few blocks (it is massive, essentially a glitch library but twice the size and with two or three towers) but I would prefer not to, Thanks.