Advanced Dungeons & Dragons: 1st Edition Players Handbook

I have chosen one of the most iconic and recognizable covers of the Dungeons & Dragons manuals:

The scene portrays a group of adventurers intent on exploring a temple dominated by a huge statue with large gems as eyes. After defeating lizard monsters, some look at a map while two try to get the statue's gems.

The whole structure works as a tower for rolling dice which, passing through a hidden path, exit from one of the two openings placed in the front.

At the top is a group of friends playing an exciting game of D&D.

In this scene there is the visual representation of a metaphor:

Behind them is a door that functions as a portal that transports players, through a roll of dice, into the world of D&D. 

Open the portal, insert dice into the opening and let the magic begins.

To close the portal just remove a panel on the back.

Between games, the dice can be stored in a convenient drawer on the back of the structure.