If you travel to La Fortuna (probably for Arenal), it is worth a morning’s time to go to La Fortuna Falls. It’s a nice hike (not too hard) and a peaceful, pretty waterfall once you get there. I recommend it. It’s a pretty long walk from the main drag in La Fortuna, so I recommend a taxi. You can arrange for them to pick you back up a few hours later, so you don’t have to wait.