Lake's Edge

The western boarder of ThunderClan is the Raining Leaf lake, one of the two lake that make up the waterfall. The lake's edge is hazardous because of its sheer cliff that drops to the lake. If a cat would fall it would be instant death because of the tall rock that pierce the lakes surface. Even if a cat would miss the rocks the chances of survial would be slim.
There is a sloping hill that goes to the lakes edge though, and the sand at the bottom feels cool between any cats feet.