Library of the Ancients

Room One: Entrance

The guardian is a permanent hurricane situated over a small, rocky island that is far from civilization. Approach by air and sea is too difficult by normal means. The storm energies have attracted numerous elementals to the region as well, and though most can be bypassed with caution, its likely at least one or two will be encountered and fought.
Room Two: Puzzle or Roleplay

The island has been swept clean so now it is bare, slippery rock. Winds threaten to carry away anything not secured to the ground. High up on one of the cliffs is a cave with flickering light streaming out. The first challenge is puzzling out how to reach the cave.

At the back of the cave is a large portal sealed by magic. A command word is required to open the valve, and the PCs should have enough clues found previously to figure it out. Perhaps it is the name of an item or NPC.

A castaway lives in the cave, though he is either out or cleverly hidden when the PCs arrive. He survives by climbing down a hidden, sheltered path that leads to a protected bay where he fishes and salvages what the currents wash up. He knows the command word but is insane from solitude and the continual violence of the storm. He craves to see the sun again - if the PCs can show him the sun hell reveal the password.

Room Three: Trick or Setback

Using the command word, a special ability, or quite a bit of destruction, the PCs bypass the portal and travel down a long set of stairs. Angry booming from wind and wave echoes through the tunnel.

If the PCs dont spot and flip a switch, the tunnel continues on until it opens up into a huge cavern full of bookshelves and dry, ancient tomes. Invaluable knowledge is stored here, as are a pair of immortal fire guardians.
The guardians are sentient and can be parleyed with. If they deem the PCs worthy, they provide knowledge of the switch back up in the stairwell, which opens an entrance to a second tunnel.

Their primary task is to protect the library from evil, and they will start torching the books if the PCs attack or if the guardians deem the action necessary.

Room Four: Big Battle

The secret passage leads down to a cave where a powerful elemental has been imprisoned. The elemental was tricked by the builders of the library and was told his realm was under attack. Over the course of weeks, the builders brought evidence that the elementals home had been destroyed. Already angry at being imprisoned, the elementals rage grew and grew as he came to believe that his home and kin were destroyed. As intended, the creatures rage was funneled and amplified until it fueled a small hurricane that surrounded the island.

The builders told the elemental his prison sentence was 1,000 years, which is true, and with that deadline and plans for revenge, his rage has not diminished over time.
The elemental is free to move about in his cave, and can communicate in broken common with the PCs if they try. Its not true that his realm was destroyed all those years ago, which can be confirmed by any of the elementals outside. If the PCs can convince the creature his realm is safe, or calm him down another way, the hurricane will disperse after a day.

Killing the elemental will be very tough. The hurricane also disperses a day after the creatures death.

Room Five: Reward or Twist

The object of the quest lies within a chest protected by the elemental at the centre of the cave. The builders lied and told the creature the last of his realms essence was trapped inside the chest, and opening the chest would release the essence, forever ensuring a new realm could not be built. This further fueled the creatures rage, the chest serving as a goading reminder, but the creature is unwilling to destroy the container as it plans to wait the 1,000 years and rebuild.

The chest can contain the object of the PCs quest, or it can contain a map and clues to the real location of the treasure, which happens to be deep inside an active volcano thousands of miles distant. It also contains a note to the elemental, in case it did break open the container, revealing the builders lies and rubbing the creatures nose in its own stupidity. This should reveal the twist of the backstory to the PCs if they opted to attack the creature and killed it. If the creature still lives it will demand to read the note, which will likely send it into a blind rage all over again, giving the PCs a bit of a dilemma.

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The five room format is simple yet allows for variety and permutation, thus its a powerful little GM tool. I feel a GM is always better off improving their dungeons by making them smaller because it gives them more planning time for clues, plot hooks, character involvement, twists, and so on.