In Ultima IV, there are three items that are require a ship so you can recover them from under the waves. Of course, this is as simple as going to the location and choosing "search." Then again, the stones you need in the same game are all in dungeons, which are kinda like ancient ruins.
But the shopkeep needs to sell it to you for 500,000 gp, then retire to his own private island. After the world is saved, of course! You should check this out, if you haven't seen it already.
This is pretty much true for most dungeons in RPG games. In reality, a castle's dungeon would be it's jail. Cells, torture devices, the works. In games, they are long winding labyrinths of corridors and rooms. May or may not contain dragons.
Homage