I was thinking of implementing this project on the "Adventure" server once its up and running (if it ever happens). Meanwhile I'm going to attempt to start it in Play World.
Rough idea: Plenty of dark/scary spots, Indiana Jones style - prepare to die and not be able to retrieve your chest (always 2 level high ceiling) - prepare to get lost - Goodies at the end - plenty of loot to make it worthwhile.
The idea is that, in case someone completes a specific quest, they are awarded certain amount of $$$. Obviously its going to be extremely hard to get all items needed to finish quest.
Here is the scale for all of you thinking about maybe helping
84 level tower
Resources needed:
25,642 Smooth or Cobble Stone
12,703 Stone Bricks
2,714 Stone Stairs
Other important + crucial to give the project some adventurous feeling

360 Redstone powders
46 Chests
56 Redstone Torches
120 Stone pressure plates
56 Dispensers
18 Buttons
6 Levers
32 Sticky Pistons
2,000 Arrows
1,000 Splash Potion of Poison
24 Iron Ingots
4 full sets of diamond enchanted armor
Just exported my schematic and placed it into Schematic2Blueprint - its now in a PDF document ready to print so i can begin with it. The schematic I built needs some modification to adjust for all traps and goodies, but it'll be good.
Anyone excited?!!
It'll be built for near admin town in some jungle somewhere - I'm getting ready still for it.
(Another side project:
http://dl.dropbox.com/u/8588808/jungle-temple.docx )