donjon noun
pronounced dän-jən or dən-jən [like “dungeon”]
: a massive inner tower in a medieval castle

Webster’s

With their magic the Greater Ones remade
The surface of the earth to their own purpose.
Cities and citadels and bridges
And tall towers reaching above,
Not one part of the earth they left un-made.
The whole world, above and below,
Even the dust and the stones
From the hollows of the earth they remade.

—excerpt from Song of the World Dragon

The Greater Ones were destroyed in the Rending. Now, only their magic and the ruins of their civilization remain. DONJON LANDS is a far-future fantasy role-playing game setting.