If you're planning on going to Rincon de la Vieja National Park, go on the trail to climb to the top of the volcano - seriously, just do it. It was definitely the most breathtaking hike of my life.
Budget 7 hours roundtrip, and bring plenty of water and snacks. Remember that the park is open from 7-4, so make sure you get there early enough to complete the hike in time. For active people (we saw a group of 60 something year olds doing the climb - but they were fairly fit for their age), this hike will still be very challenging, but the payoff is huge. The clouds roll over the mountain, you'll pass a lovely waterfall, and the peak is like a windy moonscape only seen in sci-fi movies. Once you get to the summit, you can walk around the rim to a lookout point where you can see down into the crater, which has a blue, milky sulfur lake.
Now that I've highly recommended it, there are a few caveats: this hike is absolutely NOT appropriate for children or elderly people. It is incredibly strenuous and some parts of the path at the top are narrow with steep drop offs. The wind is also VERY strong at the top. Also, at one point in the trail, there is a fork and a sign - going to the left takes you on the "strenuous"/"dangerous" path, while the right takes you on the "easier" path. A guided group happened to be there when we came upon this fork - he highly cautioned us about the "strenuous" trail, as there are lots of ridges, steep drop offs, and some people have fallen and hurt themselves/died. The "easier" path still provided the most difficult hike of my life, parts of which require you to pull yourself up a steep hill with a rope. I can't imagine what "strenuous" then means in this context.
I couldn't find any detailed trail/hiking information online when I was planning our trip to the area, so hopefully this will be helpful to would-be hikers in Rincon.