It is better to be on a rope whlie approaching the abyss of cave of swallows. The diameter on top is just 50 m, but the bell-shaped cave broadens to 150 m at the bottom. The safety line has more symbolic charkater and you should hope that the rock is solid. The depth oft he cave is 1100 feet until the first level and falls towards 1680feet to the bottom. It is called cave of the swallows, because the indigenous sailors pounce themselves by the thousands to the their sleeping places at night times.