Located in Costa Rica's central valley, some 40 km from the capital San José, Volcan Poás is one of the country's most active volcanoes, and also one of the most visited. It is 2,705 metres high and has 3 craters, one of which is known to be one of the largest in the world. The other two are filled with water and form lakes: the first is filled with cold water and the second is an acidic lake with celestial blue hues. Recently, the Poás volcano has entered a period of intense activity, and toxic fumes and sulfur are emanating from the crater. These fumes are potentially dangerous, and can also alter the volcano's appearance, for example, the color of the water in the lakes.
It's best to visit the Poás volcano in the morning - the park opens daily at 8 a.m. - to get a better view of the craters. If the weather is overcast, there will be a lot of clouds and visibility will be poor. You can ask about the weather before entering the park, but during the dry season, between December and April, the skies are often blue and clear, and you're unlikely to encounter this problem.
Nearby the Poás volcano are two other very interesting attractions, the La Paz Waterfall Garden and the Doka Plantation. La Paz Waterfall Garden is less than a 30-minute drive from the Poás volcano. Here you can admire 5 impressive waterfalls, the highest of which is the La Paz Waterfall, from which the park takes its name. To reach these waterfalls, simply follow the marked trails, a total distance of 3.5 kilometers. Once you've reached the bottom of the path, you can head back up in the opposite direction for the more courageous, otherwise you can take a shuttle bus. The park also features a butterfly house with numerous Morphos, the large, deep-blue butterflies emblematic of Costa Rica, a serpentarium, and a tropical garden with numerous hummingbirds. There's also a restaurant on site, should you wish to take your lunch there.
The Doka plantation is a coffee plantation where, if you wish, a guide can teach you all the steps involved in preparing coffee, from the picking of the beans onwards.