Originally, Ronca explained, the vie cave were carved only a few feet deep, using a rock-cutting technique first seen in ancient Egypt that involved drilling a hole into the tuff, inserting a piece of wood and then filling the hole with water. The wood would expand, forcing the tuff to fracture. They would do this again and again, lengthening and deepening the road to its desired size. "It"s not a simple and easy technique," she said.