One of the must-do things in Arenal is getting into Hot Springs. Most of the hot springs are in resorts where you pay a certain fee to get into the hot water. There is a place where you need not pay any entrance fee. It is a river/stream near Tabacon which has the same warm water that goes into the resorts.
It was already pretty dark when we reached the spot. We parked our car on the side of the road. We got off the road and less than 50 meters away we reached the springs. It is one of the coolest experiences I ever had. A warm river. There was moonlight. People had brought candles and it made the entire scene magical. We spent a lot of time in the water. I met many people there and I even taught a couple of guys to speak Sanskrit. One of the best evenings of my life.