"While, at a sign from you, sire, the unique and final city raises its stainless walls, I am collecting the ashes of the other possible cities that vanish to make room for it, cities that can never be rebuilt or remembered."
- Italo Calvino, Invisible Cities
North of Canterlot, in the far marches of the Equestrian lands near the border with the Griffon tribes, there is a mountain that flies.
It is not shaped like the mountains adhering to the rocky earth far below. It is not shaped like the easy geometric summits drawn in foal’s storybooks. It does not share their snow-capped peaks or bedrock roots. There are no veins of ore running through it like blood. It cannot be climbed.
But it is a mountain, nevertheless.
From below, Derecho appears as a massive stone hanging in the sky. It is vaguely diamond-shaped, with two tapered poles pointing toward the heaven and the earth. Here and there, visible as it slowly rotates, sharp angles and straight lines still hold their shape, but time and weather and the relentless hail of solar radiation have eroded much of the rest, transforming it into a landscape of runnels and abstract sculpture.
A wall a thousand feet high girdles the mountain like a belt around its middle. This wall has survived somewhat better than the rest of the structure, for the pegasi who created it used the densest, hardest clouds their magic could manufacture in its construction. Still, even these clouds were not meant to withstand the centuries, and they have begun to crumble, leaving the thousand-foot high wall significantly shorter in spots. The upper edge of the wall has suffered more than the lower, which remains almost perfect for its miles-long run.
Tiny spikes dot the wall at regular intervals. Pegasi who dare to fly closer may see these specks resolve into towers, placed there for the city’s defenders to rest and, if necessary, take shelter from the harsh weather of the north. Most have crumbled. A few seem untouched. Again, the towers hanging from the bottom of the wall have fared better than those above.
By itself, this wall would be counted among the largest cloud structures ever created. When it was still intact, its cubic volume was greater than the entire city of Cloudsdale.
Seen against the entirety of Derecho, of the mountain it rings, the wall is little more than a thin band. A white ribbon, once satin, now laced with holes and imperfections.
It is fair to assume that the first pegasi who dreamed of Derecho could not imagine the enormity their creation would become. Few records remain from Equestria prior to the Unification, and besides, pegasi were never renowned for their bookkeeping.
Deep inside Derecho, in the heart of the mountain, there remains a small compound, made of thick cloud walls with thin, high windows just wide enough for an arrow to pass through on its way out. Once, these windows stared out at the high airless reaches facing the Griffon tribes. From these windows, pegasi could see the sky and the ground and everything between. It is small, barely twenty paces across, with only three rooms.
From this tiny seed, the mountain was born.
* * *
Unlike most cloud cities, Derecho is not white. The pegasi who built it over the course of centuries packed its structure hard with water, turning it the color of a thunderstorm. Over time, the lighter clouds – the streets and houses and parks – dissolved and blew away, leaving only the city’s bones behind. Foundation clouds a mile deep still hold their form remarkably well, and give Derecho its characteristic diamond shape, like a pair of ziggurats joined at their base.
Derecho is so large that its two poles experience different weather. Wet air, driven by the wind into the upper half of the city, is forced further upward, causing it to cool. This forms clouds, which in turn form rain that runs down the city’s slopes in a constant stream that becomes a waterfall when it reaches the city wall. Mist perpetually shrouds the top of the city, turning Derecho’s peak into a nebulous dark shape more imagined than seen.
The underside of the city, by contrast, is dry. The mountain above intercepts the rain like the world’s most inefficient umbrella. The cloud walls and bricks have dried and turned brittle over the centuries, and they tear like paper.
When it was still inhabited, Derecho held station at the border between Equestria and the Griffon lands to the north. It did not drift with the winds, as it does today. It and its shadow were ever present.
To the earth ponies living below, Derecho was a mixed blessing. It kept away the griffons, as was its intention, but earth ponies as a rule prefer their mountains to stay on the ground.
The earth ponies did not talk much with the pegasi back then, except to trade food for favorable weather. They did not know the pegasi called their fortress city Derecho. They did not know pegasi named their great cities after storms. Instead they gave it their own name, one spoken with both derision and awe, in honor of the weight of its shadow on their backs.
They called the city Eclipse.
The pegasi did not think much of the earth ponies below them. Most didn’t realize they were there at all.
* * *
Derecho’s construction took centuries. Swaths of Equestria’s northern territories turned to desert after the pegasi stole their clouds as building blocks. Some of those deserts are still there today.
At the height of its power, nearly half the souls of the pegasus race resided in Derecho. The Thunder Queen ruled from its highest spire. Cloudforming became a true art in Derecho’s halls, and today the Derecho style of sculpture remains the most widely imitated throughout the world. The largest library ever built by pegasi, containing over a thousand volumes, is said to have existed here.
As noted earlier, the pegasi were not known as bookkeepers.
History records two instances of Celestia visiting Derecho. The first, in the decades leading up to the Unification, was a diplomatic visit by her and Luna with the notionally equally ranked pegasus monarch at the time, Hurricane III. Her daughter, Hurricane IV, was the first of their line to rule the pegasi from the new unified capital, Everfree.
The second visit was centuries later, shortly after Nightmare Moon’s banishment, by which time Derecho was already derelict and abandoned. No accounts exist of this visit except for a single line in the Canterlot Sun Court’s daily proceedings, noting that the princess had departed for a short trip, and returned by sundown of the same day.
* * *
Modern sky maps do not show Derecho as a fixed point. Instead there is a line, showing its gradual course across the northern territories, with dots occasionally marking a date when the city was spotted at its new location. After the most recent date, the solid line becomes a dashed line, the product of the best guesses of pegasi forecasters for its wanderings.
Nopony calls Derecho home today. Pegasi sometimes visit to explore its depths or relive the glory days of their race. Most leave soon, realizing how little comfort glory is.
And Derecho, the Mountain that Flies, the Fortress City of the Clouds, continues on its silent way, a mass of bones and ghosts floating ever into the future.