The Dark Tower of Cabilar is an D&D adventure for 4-8 characters of 4th-7th level. The party should have several fighters and at least one magicuser, thief, and cleric. Magical weapons are required. Note that falling damage is calculated as increasing by 1d6 damage per 10′ fallen.
With a little imagination, converting to DnD 5e, Pathfinder, etc. should be very easy for any Dungeon Master, but if you need help on conversion to 5e, I created this page for such an occasion: Convert Old Dungeons and Dragons Adventures To 5e