This is known to be the largest cave network in Cuba and it is pretty big. The guided tour is worth a visit. There is a nominal fee for entrance and they provide you with helmets and torch lights. It is a fairly easy tour and the hike does not involve portions that are too steep. As long you are wearing a good pair of sports or climbing shoes, you will be fine. I did it in beach chappals and still managed to get away with it :) There are far better caves else where (recommend Mexico and Budapest if you really like caving), but this is still worth a visit if you are in Vinales. Just make sure you bargain for the taxi to get here so it does not end up being too expensive.