Here's a breakdown:

* Caldera: A large, cauldron-like volcanic crater, typically formed by the collapse of a volcano's summit after a major eruption. It's much larger than a typical volcanic crater.

* Volcanic mountain: A mountain formed by the accumulation of lava and ash from repeated eruptions.

So, the scenario you describe – a huge hole left by the collapse of a volcanic mountain – is a caldera.

Here are some additional details:

* Calderas can be incredibly large, spanning miles in diameter.

* They often fill with water, creating beautiful lakes.

* Some famous examples include Crater Lake in Oregon, USA and Yellowstone Caldera in Wyoming, USA.

Let me know if you'd like to learn more about calderas!