El Vado is one of Oaxaca's hidden treasures. I was able to experience the beauty of this place on my last family trip. El Vado isn't one of the tourists attractions you would find on a book guide. It is about a 2.5 hour drive south of Oaxaca city center to San Sebastian de las Grutas. The drive is bumpy and the road has a lot of curves so if your stomach is weak I would take that into account. But view through the drive makes its totally worth it!
There will be signs guiding you once youre getting closer, when you arrive to the top of the hill there will be a sign "las grutas". There you will find logged cabins and can get a guided tour of the caves which are in a natural state for about 30 pesos. This area is truly breathtaking and worth the trip if you have already seen everything else Oaxaca has to offer.