For me, a good dungeon location has to have the following:
- The place must have at least once served a purpose outside of being a time sink for the player to explore. Games that have "dungeons" that are basically vast expanses of randomly meshed hallways, I'm looking at you.
- The dungeon must have a believable, non-constructed reason for a player to choose to explore it on their own. Something being deliberately placed down there, then the player being sent on a fetch quest to find it, does not count. However, it does count if the item has a believable reason to be there, and the player is/can be sent in to go get it.
Drake Dens
Location - General Dinyoran. They prefer caves at high altitudes when available but will settle for any enclosed structure of appropriate size.
Dangers - The drakes, of course! Drakes do not hunt in packs smaller than 5, and each pack shares a single den. Pack sizes can be as large as 30 members. Drakes are highly territorial and will not back down once challenged. If you dare enter a den to collect its spoils, be prepared to kill all of them.
Treasures - Miscellaneous. In their radings, Drakes don't discriminate in what they steal. They take whatever they can get their claws on, then sort it all out later. They eat the food, then stash the rest in their lairs in sort of a "trash pit."
Serek Tombs
Location - The black desert of Maurogc. A few have entrances still available on the surface, but most are now long-buried and their only available entrances are those created by unlucky miners.
Dangers - The Serek Tombs are filled with hordes of undead to protect against the desecration of the tombs of their ancestors. They do not dwell far outside of their resident tomb, but will fight against any and all intruders. A single tomb can contain thousands upon thousands of soldiers, consisting not only of the original guardians but also the risen bodies of intruders who were slain. Do not enter unprepared.
Treasures - All of those undead soldiers are controlled and maintained by an artifact called a Gadtanet, bound with a powerful demon. The process of creating them has been lost to the mists of time, so one retrieved is absolutely priceless. As an additional bonus, taking the Gadtanet out of the tomb will cause all the soldiers inside to cease functioning, making it safe to re-enter the tomb to take various other treasures, such as the offerings of gems and gold given there.