Spire the Infinite Palace
Imagine you are standing on the crumbling edge of a great stone bridge. Before you, facing out beyond the old stonework is an endless blue void in which clouds scut and swirl lazily, above and below a hazy nothing. You turn and look along the bridge, littered with stone slabs askew, the construction is ancient but sturdy save it is only half a bridge at best, jutting out into the sky behind you. Beyond the bridge is a massive stone wall, adorned with leering faces and noble figures, gargoyles and statues. A great copper door, soft green with it's age lays cracked open, the opening large enough to admit ten men marching shoulder to shoulder yet it barely looks like a mouse could squeeze through given the distance you are from the door itself. You cannot help but look upwards to see the vast conglomeration of architecture stretching up into the hazy distance, turning into purple and blue as though you're looking at some great mountain range fading into the beyond. Your mind finding it difficult to explain just how vast this strange structure truly could be. Looking to the side, the same structure stretches off, until it becomes obscured by its own protrusions and crenelations seeming to curve away from you even this far out away from it on this lonely bridge.
Spire is the dimension of Fortification, Edifice and Adventure. The spire itself is a a seemingly infinite tower of vast size , a conglomeration of many styles of castle, palace, fort and more, joined together into a jumble that forms a vast and impossible acropolis stretching far beyond any possible reason.
Somehow civilization clings to this Spire, from small villages built in large halls and hidden courtyards to the vast "City" of Redoubt which brings together many thousands of people and hundreds of species in a vast network of jutting battlements and enormous city like fortifications. All centered around three Grand Portals that lead to two Prime Material planes and the Elemental plane of Air. It is here that the Cartographers Guild has its headquarters. Hiring adventurers to delve and explore the hidden depths of the inside and core of the Spire as well ascendaning or descending the surface.