I would go about it as;
Contact Other Plane - Who wants to keep a volcano open? Karakatal? You up for it?
Conjure Elemental - Hey, my dude! Uncle Karakatal said you're the... entity... for the job!
Wish - Properly worded, perhaps after visiting a sage with elemental planar knowledge, to seal the deal.
You then have permanently bound a willing elemental that will frolic in the newly renovated Phlogiston Baths and Spa! It may have some friends over, from time to time. Hope that's not an issue.
[May cause prolonged madness or the ire of extraplanar entities. Loss of rubies, rare incense, and material wealth is a known side effect. Please consult your cleric with any curse-related issues that may arise.]