From the back of the box
Have you ever wanted to break the chains and design your own AD&D adventure scenarios? Well, this is your chance to do it in the incredible FORGOTTEN REALMS game world, with your only limitation being the size of your hard drive.
Build maps with the easy-to-use grid screen and link them with teleporters, doorways and stairwells.
Choose your characters from the massive bank of 112 monsters and multiple non-player characters.
Design the dungeons of your dreams and test them as you go with a point-and-click interface that makes errors gone forever -- at the touch of a button!
Test your mettle by playing a pre-created scenario, The Heirs to Skull Crag, with four separate quests to solve. Should you choose, you can even modify this ready-to-go adventure.
UNLIMITED ADVENTURES is, in a word, fantastic!
From Wikipedia
The chief feature of interest in this computer role-playing game is that it contains an editor that allows the user of the game to create new adventures that anyone else who owns the game can play. The game uses a variant of TSR, Inc.'s Advanced Dungeons & Dragons rules in the gameplay. The engine within which adventures are played is based on the "Gold Box" engine that made its debut in the game Pool of Radiance, although some improvements have been made (for instance, the color depth has been increased from 4 bits to 8 bits). Despite possessing features that, today, are considered limited (such as a 320×200 pixel resolution), the versatility and ease of use offered by this engine have created a community of users who remain active to the present day.
More than seven hundred adventure designs have been created for this game. They vary widely in quality, and the best of them are comparable in depth to the original commercial releases.
Source: Wikipedia, Forgotten Realms: Unlimited Adventures , available under the CC-BY-SA License.