Oddly enough, the side of an active volcano turns out not to be the safest place to live. The last major eruption of Pacaya Volcano, not far from Guatemala City and Antigua, caused considerable damage to nearby villages and reshaped the summit. It scattered volcanic ash over much of the nearby area, prompting school closings and emergency evacuations and cleared much of the vegetation near the top of the mountain. That May 2010 eruption, though, didn't convince some of the local hardy souls to move away.
Only about an hour outside Antigua, and not much farther from Guatemala City, Pacaya Volcano is a popular hike for tourists. There are quite a few active volcanos in this neck of the woods; you can see two others from Antigua. Along with Pacaya, they're all part of what's known as the Central American Volcanic Arc.
The top of the mountain is constantly changing, with each episode of volcanic activity changing the shape and nature of the summit. There's currently no classic crater to peer into, and the nearest you can get to the top is still a few hundred meters below the peak. The gravelly volcanic rock that covers everything up there is warm to the touch, and steam still steeps out steadily. When I went there was no flowing lava around, but it's an active volcano and things can change quickly.
Photos of Pacaya Volcano
What to Know Before You Go
It's a strenuous hike on uneven and steep trails. Wear good, closed walking shoes with good tread. Sandals or flip-flops will be no good--the fine volcanic gravel and sand will rub and the volcanic rock can be very sharp. The weather at the summit can be quite different than further down the mountain, so be prepared for clouds or rain to roll in very suddenly and for it to be significantly cooler. A flashlight is a good idea, just in case. A walking stick will help--you can rent them from the kids at the trail head for about 5 quetzals. Take water with you--there's none available at the summit. Early morning is usually considered the best time to go.
Travel Advice for Guatemala
You can find the latest U.S. Department of State travel advisories and information for Guatemala (such as entry visa requirements and vaccination requirements) here.
Health & Vaccinations
The CDC makes country-specific recommendations for vaccinations and health for travelers. You can find their latest information for Guatemala here.