The Azores are basically volcanoes that stick out of the Atlantic Ocean. The fact that these volcanoes haven't faded out yet, is proven at least by the eruption of the Capelinhos Volcano in 1957.
This panorama was shot on the Furnas Volcano on the island of Sao Miguel. This volcano had its last eruption 5,000 years ago, but it still shows activity in numerous forms. At many places in the area of Furnas you can smell clouds of sulfur and see natural boiling water and mud. The boiling water sends of big clouds of steam into the air, adding greatly to the spectacle.
The air and steam escaping the holes in the ground is rich on minerals and has a ground temperature of about 130 degrees Celsius. So stepping over the fences like I did is ill advised, especially if you wear open shoes. On weekend days the steam pits and the lake can get crowded with locals. The locals bury cooking pots around the steam pits for naturally cooked (and probably somewhat oddly flavored) food.
Directly next to the steam pits lies Lake Furnas, the serenity of which has much contrast to the "smells and sounds of hell" the steam pits produce.