Poas Volcano, located in the park of the same name, is one of only a few active volcanoes that you can get incredibly close to if you walk. It's supposedly quite a site to see, if you happen to go when it doesn't look like this. Driving there was fun, the walk up to the crater is very easy and well-kept, and the observation area is enormous. My advice: check the weather before going so you don't arrive in a rain storm with ZERO visibility, like me. Dress warm too, it's so cold you can see your breath up there.