Why is Trump threatening to bomb Iran's Pickaxe Mountain?

The war in the middle east is intensifying. Over the past two weeks, in the wake of a failed ceasefire, the US has escalated strikes on Iran, and so too has Iran on shipping, and its Gulf neighbours. President Donald Trump says the US isn't finished. He's warning American forces could soon target a location known as Pickaxe Mountain, near Iran's heavily damaged Natanz uranium enrichment facility. So what is pickaxe mountain and why is Trump talking about it?