Back when we had a farm we had an old barn that we did a few renovations to. We decided to break through the solid 3 foot thick stone foundation wall on the north side in order to create a much needed opening into the barn.
I rented a jack hammer and worked for nearly a week trying to bust away enough stones and mortar just to make a modest size opening for a small horse to walk through. I realized then how much stones like to hang on. Even after the hole was drilled and chiseled large enough to reach in and pry on chunks of the loosened masonry, it was still a battle to actually remove any stone from the wall.