This is another trick I stumbled across when I was a kid. Whilst playing Ultima IV one day I was wandering Britannia. I left Britain and just for grins I took out the Britannia disk and stuck in the Dungeon disk. I walked east toward the bridge and when the game loaded the next map segment from the "Britannia" disk, I ended up with it being all dungeon stuff. It was mostly impassable, but I did find a way into it. In there I came across a chest. It had gold inside, and best of all.. it didn't disappear or empty
I kept opening and opening and opening until my money was maxed out. Took damage from traps, but maxing out my money was worth the healing. Threw the Brit disk back in and went back west and all was normal.
Another trick I saw was once in town throw in the Keep disk then go up/down stairs. It will load a keep/town style map but it will be populated with random characters and weird stuff. It's amusing. To get back to normal, throw in the town disk and ascend/descend some stairs.