Playa Ventana is located between Uvita and Ochojal, about 15 minutes from the Casa Verde. You will have to keep looking out for signs on your right, then enter a small road. At the end of the road, you will have to walk the last bit to the beach. The beach is truly beautiful, not only because of the many coconut palm trees (which by the way serve as great snacks for in between if you are good with getting the coconuts open) but also because of the amazing caves which fill up with water depending on the tide. Its also a good beginner surfing beach as well as good for swimming. When you park your car, do not leave any belongings in there though and pay the small "parking fee". Also, try the ceviche on your way out on the right hand side on the costanerra. Its known to be one of the best ceviche in the entire south!
I first came to Costa Rica in 1998. I fell in love with the country right away for so many reasons. I have been coming, living and unfortunately never staying off and on since.