There's this place called the Walk. It is a 100 foot long isthmus, ending in a 50 foot (in diameter) circular island. This isthmus is five feet wide, mostly. It would be just a normal old place, except for the fact that its also happens to have 30 foot cliff on either side. This makes it a 100 foot long hard rock, five foot long bridge, with pebbles tossed on top. And, of course, the huge waves crashing onto the sides with regularity, making the whole thing wet. Falling is not an option, because of the aforementioned huge waves crashing against solid rock. On the island (of sorts) itself, the rock has some tunnels. This is where a tribe of orcs set up their base, and this is where a famous treasure lies.
Room One: A Stroll in the Park
The Walk, as it has come to be called, was dangerous before a bunch of orcs took over and set up a catapult to fire boulders at all who come. Now it is very dangerous. The orcs will continuously fire either a single large stone or a number of smaller stones. Added to the danger of a catapult is the Walk itself. 100 feet of pebble strewn, wet rock. Running carries the inherent danger of falling the 30 feet into the ocean, which will result in death, from either the fall or from the riptide throwing you against the cliff wall. Every so often, probably 10 feet or so, either a scoop in the path from a boulder hitting the walk, or the boulder itself, will present an obstacle. Also, the group of orcs firing the catapult include a wizard, who will block any attack spells like fireball, and an archer, who will shoot at people who get too close to the catapult. The final 10 feet should be blocked by a boulder, to give the PCs (if they chose to run across the Walk) a place to come up with a plan concerning the Catapult Crew.
Room Two: Down the Hatch
The Catapult Crew consists of one archer (who has a sword), one wizard, ten warriors, and a runner. The runner's job is to get down the trap door, and raise the alarm, while the rest block the intruder. The orcs who remain to fight off the PCs while the runner heads down the hatch should be good enough to provide the PCs a challenge, but weak enough so that they will die. Either way, if the runner gets down the hatch before the PCs can stop him, and ring a bell in the tunnel below, the orcs will attack in mass, which would mean that the PCs should run. The Catapult Crew will have no money. They will also, especially if its night, play poker.
Room Three: A Hall, a Sentry, and Failure
Down the hatch, there is a tunnel. In this tunnel is a bell, which the runner in Room Two was heading for. The tunnel will lead to the orc's hall. Its 40 feet wide, and 10 feet tall. To the north, east, and west are ladders leading to sleeping quarters. They are labeled in orcish. To the south is a ladder leading to the treasure. In the center of the room are more guards. They will be playing poker quietly while the real guarding takes place in the shadows. In each corner, which are draped in shadows, a guard waits quietly. Each of these guards will run to warn the others if the PCs are sighted. The guards playing poker will draw their weapons and attack. These guards should be easily beaten. They, too, will lack money.
Room Four: A Treasure, of Sorts
Down the southern ladder is the treasure vault. The others lead to sleeping quarters. The treasure vault is a library. Inside, each wall will have a shelf full of books. Inside here, feel free to dispense certain books containing hints of quests, or have someone send the PCs to collect a certain book. Either way, there will be a table with an open book and a lantern down here. The lantern will be unlit. The orcish army will follow the PCs after a couple of rounds (give the orcs 10-20 minutes of in game time), and the PCs will meet Chief Graf. The Chief is a half-orc, which shows why the library isn't a pile of cinders. He will explain that he, too, was first drawn by rumors of a treasure, like the PCs, only to find books. He likes to read, which is why he kept the library intact. He will know send his orcs after the PCs. The orcs should not look like they are beatable. Whether they are or not, the PCs should exercise a technique that they may or may not have mastered: Running Away. A tunnel will wind down and down. It should have a couple of traps that will slow down the orcs more than the PCs. The PCs should take it. The tunnel will exit out into Room Five.
Room Five: Something More Precious than Gold
A dock lies at the bottom of the tunnel, hidden through illusions that no one would get close enough (huge waves, remember?) to find. It has a sailboat accessible, with bottom deck with 10 hammocks and a small pile of gold. Not a fortune, but a little something to make the PCs happy that the whole thing was not in vain, and to cover expenses. The boat will take a bit to cast off. In the meantime, this seems like a perfect opportunity to perfect ones fighting. The orcs will come before the boat is ready to set sail. Good thing the tunnel makes it so only two orcs at a time can come out.
Epilogue: And they sail off into the sunset...
And the PCs sail of into the killer waves determined to throw them onto the cliffs. Or use your godlike powers to make the waves peaceful for the PCs to get some good "and-they-sail-off-into-the-sunset" -ing.