Have a dungeon that could fit anywhere? Want to get the heroes there in a hurry? Try this.
A wishing well is nothing more that a place to hope and dream. A token offering is given with the silly notion that the wish just might come true. But what happens when these wishes start to come true, on a regular basis?
A secret MLM (pyramid) company that offers eternal life, but in fact it transfers the life forces of its members to those position "above". If you get high enough, (meaning you get enough new members) you start to enjoy the benefits. Maybe a willing sacrifice is much more effective for the transfer. But no one says, that a suddenly unwilling member, threatening to tell the authorities, may not loose it involuntarily... thus start people to vanish, and aged corpses are deposited somewhere safe.