The Black Crater is a landmark within Wizard City. It itself is the product of a magical mishap the approximate size of six city blocks. To this day, nobody is exactly sure what happened, though it has now resulted in site of pilgrimage for those visiting whispering prophecies of the Pit of Portents and/or those wanting to throw things down the bottomless pit.
The entire desolation is a spongy black-as-soot waste. Nothing grows in it. Nothing can be built on it. Anything spending inordinate amounts of time standing still in the Black Crater simply sinks into the ground at a pace of 4cm / hour. This has given rise to the speculation that the Crater is in fact a portal to another dimension, and that might be true.