I can see it now... an elven caravan arrives in the spring, searching for the dwarven fortress but coming upon a high wall.
Elf Merchant: Ambassador, it appears the dwarves have walled themselves in.
Ambassador: Perhaps they are building some sort of secret device, and do not wish it reveal unduly. They can be an odd lot, to be certain.
Elf Merchant: Of course, your Eminence. That makes perfect se- what was that?
From the top of the wall, water begins running down the surface, and suddenly rushes over in a wave, washing the elves and their goods away, and drowning the Ambassador.
Dwarven Messenger: Baron Urist von Mandatebeard? There is news of the surface project.
Baron: Go on...
Messenger: It would seem that a section of the eastern wall was constructed somewhat shorter than the rest, and water ended up spilling over when the elven trade caravan arrived, drowning them all and destroying their goods. We have begun a tomb...
Baron: Excuse me?!
Messenger: *ahem* We have begun construction of a tomb for the sentry who was standing on the wall nearby at the time. It would appear he was laughing so hard he fell off, sir.
Baron: I see. What was his favorite gemstone?
Messenger: *checks clipboard* Degel preferred star sapphires, sir.
Baron: See to it that his sarcophagus and statues are encrusted with them.
Messenger: Right away, sir Baron.