Now, in League of Legends, there's three "rings" of turrets before the inhibitors, the outer turrets, the inner turrets, and the inhibitor turrets. Typically, you'd take these in order, taking the outer mid turret before the inner mid turret, and the inner mid turret before the inhibitor one. This is due to the fact that minions are key to actually hitting turrets without dying a very quick death, and they reach said turrets in precisely that order.
That said, is it possible to break the sequence? If you take a late game team that doesn't mind taking the turret shots, could you run straight past the outer turret and just start beating on the one behind it? Or do turrets behind the front lines have invincibility? (Much like how the Nexus turrets can't be harmed unless there's an inhibitor down, and the Nexus can't be taken until the turrets are gone.) Obviously it wouldn't be a smart tactic (outside of very rare base race situations), but I'm curious if it could be done.