Does this seem viable...

Does this seem viable? Has anyone toyed around with the idea of creating a safe dungeon to house an ecosystem in there that could be of use for the outside world? What could it be used for? How can this go wrong?

>a safe dungeon to house an ecosystem in there that could be of use for the outside world?

So a low-maintenance farm. Quickly rendered obsolete by the more labour-intensive, but far more productive regular farm.

Seedbanks, mostly

My mind immediately went to BDSM.

I've been corrupted.

No, you're just normal for someone on Veeky Forums.

>regular farm
Can you farm dragons there?

It's pretty much the same as farming, only you're farming monsters.

Producing free light, heat, soil and so on are absolutely trivial for a wizard and druid working together.
Whatever layout the original dungeon had, it can be rearranged within days by using stone to mud and mud to stone strategically.
The best thing to produce would be pesh or whatever narcotic catches a good price in setting.
Several layers of underground farms can easily feed a castle during a siege.
A well designed dungeon can become self-sufficient with minimal effort, and that's before you start opening up portals to produce goods out of thin air.

What is a dungeon to you? Just any underground structure? Then the answer is yes, there are safe dungeons all over the real world. You probably have one in your basement.

That's probably a more typical use of the word 'dungeon' by non Veeky Forums standards
to go a step further producing ANYTHING with a druid and wizard working together is pretty trivial