About a week ago I ran over one of my customers lawn with the Super Z, mostly just cutting up a few leaves. Flat yard, no nothing around but grass. Out of nowhere I hit this hole with my rear tire that I never knew was there, about a foot deep and long. Didn't think much of it other than - DAMN! .. what was that? .. and went on. Well today the owner calls and asked if I found a hole in the yard .. "yea, about a foot deep ..", THE HOLE IS NOW 8' DEEP, 4' ACROSS!! He said I hit the edge of an old tree stump and the ground has just caved in. Whew - could have spent the holidays down under! Careful out there, never know what you'll find in some yards.