Fatal smell of sulfur and barely visible through the fumes! The Das Caldeiras Lake is one of the most typical images from the Island of the Azores. Personally I have never enjoyed that image of steam rising from the earth below, and the obnoxious smell of sulfur coming from every corner of the place. The steam is due to the passing through two banks of very hot water, and a the cold one and the abundant iron in suspension. In fact its waters are so hot that they have opened a spa with a hot thermal swimming pool.