The Valley of Furnaces was a strange place at spawn, made out of a cluster of hundreds of Furnaces and lava poured over everything.
A long time ago (probably late 2010/2011), someone placed a cluster of furnaces not so far away from spawn and surrounded those furnaces with lava pillars and cobble monsters (which makes the valley of furnaces well known). No one knows how much coke the person must have sniffed to make this, but on thing is know for sure... it's near spawn, and it has alot of furnaces. The earliest description of the Valley we have is from THEJudgeHolden's comics.
In 2017 the valley was griefed by some unknown autist. PandaPimp decided to turn it into a valley of ender chests.
In early 2018 some unknown autist (Probably the same one from before) stole most of the furnaces and ender chests and put cobble swastikas everywhere. Today, the site has become 'anti-griefed', by that I mean that the Valley has been (mostly) cleaned off of its Furnaces, Lava, and Casts.