Poás is one of Costa Rica's most accessible active volcanoes and one of its most popular day trips from San José — just 55 km north of the capital by a winding road through coffee plantations and cloud forest. The main crater, 1.3 km wide and 300 m deep, is one of the largest in the world and usually holds a pale green sulphuric lake that steams and occasionally throws geysers of acid water. A short paved trail from the visitor centre brings you to the rim in ten minutes. A second, quieter trail leads through stunted cloud-forest to Laguna Botos, a cold, extinct crater now filled with rainwater.
Visit early. Poás makes its own weather, and by mid-morning the crater is often swallowed in cloud. Aim to arrive at opening (around 7 am) for the best chance of a clear view, and bring a jacket — at 2,700 m it is noticeably colder than San José. Access is restricted when volcanic activity spikes; always check the park status before driving up. The whole visit takes under two hours, making it easy to combine with the La Paz Waterfall Gardens on the way back down.