The Guatemala City "sinkhole", about 60 feet (18 meters) wide and 300 feet (100 meters) deep, swallowed a three story building in an almost perfect cylindrical hole. A burst sewer pipe or storm drain probably hollowed out the underground cavity that allowed an underground cavity to form.
The hole appears to have been caused by the deluge from tropical storm Agatha blocking sewerage pipes. Spill water gushed away the underground. Guatemala city is built in a region where the first few hundred meters of ground are mostly made up of a material called pumice fill, deposited during past volcanic eruptions. And just like loose gravel can be washed away by water, so was the underground in this spot. (Full)
With thanks to Juan for the tip.
Picture courtesy Paulo Raquec, National Geographic.