Those things are damn powerful.
I was flying into KIX
one evening. It was dark and something similar to those lights (they are common on top of pachinko parlours) was in operation. We must have still been at around 6000/7000 ft. Maybe even higher. As it twirled around we flew directly through its beam several times. It was highly visible as a very bright spot on the ground.
Made me wonder if we would have been visible from the ground, lit up by search lights WWII style.