Hide it on the other side of an archer tower or CC. usually they can block the view of 1 wall.
Printable View
Just hide it behind an archer tower or town hall.
Accidental upgrade of walls, ey? Once you've done one, you'll have to do the rest. Supercell has latched onto your OCD and now wants you to spend a few hundred bucks on buying gems so you can spend 1 billion gold/elixir upgrading the rest! Have fun :smirk: