"It is in the desperate moment when we discover that this empire, which had seemed to us the sum of all wonders, is an endless, formless ruin, that corruption's gangrene has spread too far to be healed by our scepter, that the triumph over enemy sovereigns has made us the heirs of their long undoing."

- Italo Calvino, Invisible Cities

West of Canterlot, beyond the Galloping mountains, beyond vast rolling plains filled with waving grass, beyond a desert painted with the pastel colors of a faded rainbow, beyond the last town and the last road and the last tree, the world comes to an end.

It ends on a high cliff overlooking the largest body of water known to any mortal race. This great ocean extends beyond the horizon, limitless and incomprehensible. The few pegasi who fly this far from the comfort of civilization say the air above it tastes alien, and the clouds that drift in from its shore mock their attempts to shape. It is a wild ocean, and cruel.

The unbroken cliffs extend to the left and right as far as the eye can see, and pegasus eyes can see quite far. The edge of the cliff is a knife that cuts the world in two. There is only one imperfection along its entire thousand-mile run.

It is a tower, and it is visible from dozens of miles away. The spire at its top appears first as travelers approach; the curve of the planet conceals the rest.

By the time travelers reach its base, the tower seems to reach the heavens. The flat earth that extends to the east and the flat ocean to the west only emphasize its unnatural height. Clouds break against its side and drift past, like bits of cotton caught on a bramble in the woods.

The tower’s walls are not perfectly regular. Three grooves, each the size of a city block, spiral up its length, lending the entire affair an organic feel that is utterly defeated by the tower’s monstrous size. At its circular base, the tower is hundreds of yards across; Celestia’s castle atop Canterlot Mountain could fit easily within its circumference. A slender but noticeable taper begins at about the height of the lowest clouds and ends miles above in a tip that was once as sharp as a needle before centuries of wind and neglect wore it down to a blunt and misshapen lump the size of a pony’s hoof.

A closer inspection of the walls reveals hairline gaps between massive blocks of granite. They are polished smooth, and even the long years alone with the wind and the ocean have done little to weather them. Salt stains the side of the tower facing the ocean a splotchy white that vaguely resembles the cloudy sky above.

The architects of the tower considered it their race’s greatest work, though not a single unicorn ever lifted a hoof in its construction. It was the seat of their power, the heart of an empire that extended no more than a dozen miles in any direction but held more wealth than the entire rest of the world combined. For a dozen centuries the White Queen ruled from the tower’s silver throne, and they believed, in their hubris, that the dream would last forever.

It did not. No unicorns remain in the Heartspire. The only souls here are ghosts.

But there are many of those.

The base of the tower is interrupted by three openings. They are not doors or gates, for they were never meant to close. The Heartspire was not intended as a defensive structure.

The first level of the tower is a vast open field. It held gardens once, filled with plants and animals from every biome in the world. Warding spells contained small patches of desert, swamp and tundra, all within a dozen feet of each other. All were beautiful, yes, but beauty was never their point.

This is power, the gardens said. We can bend nature to our will.

Little grows here now but weeds. It is dark on this level, and only plants adapted to the twilight places of the world thrive in the ruins. What little light remains leaks in from the openings and from faint flickering stars high above.

The stars once shone like miniature suns. Although they appear like pinpoints from the ground, each is a crystal globe three feet across. When they were new, they were so bright that any organic object that came within ten feet would burst into flames. One of these globes, by itself, could light an entire town at night.

Most of the globes are dead now. The few that retain a bit of their ancient magic appear ready to fail at any time.

It is an illusion. They will all live longer than the pony watching them far below.

Along the distant walls, wide ramps slowly wind their way up the tower to the levels above.

Most of the Heartspire is filled with residences. The smallest homes are near the bottom, though most of them would seem lavish by the standards of modern ponies. Higher up, after the spiraling ramps have circled the tower several times, the homes are as large as palaces, and still they grow larger, until each level of the tower can only hold one or two. But these homes are like castles, complete with their own walls and towers, built in mockery of the ponies living far from the Heartspire’s walls.

You build walls out of fear, the castles said. We build them for joy.

Almost no light naturally reaches these levels. Unlike the open fields below, there are no sunglobes to push back the darkness. Each home was expected to provide its own light, and in any case the unicorns living within them filled the tower with illusions of star-filled skies, perpetual sunsets, or whatever scene they desired. The tower had no real windows, which would have spoiled the featureless perfection of the walls.

The highest residence is virtually a city unto itself. The tower is narrower by this point, but it is still wide enough that the far side is lost in darkness. Hundreds of small outbuildings surround a central castle, and the rotted remnants of flags hang limp from its pinnacles in the still air of the tower.

Still the ramps lead higher. The Heartspire is not even half done.

The next level is as open as the first. The ramps end on a smooth plane of stone that stretches the entire width of the tower. Hundreds of yards above, a vaulted ceiling carved with images of stars and galaxies stares down at the emptiness.

In the center of this empty field rises a pedestal dozens of feet high. Stairs inlaid with every imaginable precious stone and metal lead up its side to a top just a few feet across.

There was a throne here once. It was crafted from silver and platinum, with a red velvet cushion said to be softer than the very clouds. During the Heartspire’s long reign, ninety-seven mares styling themselves the White Queen sat here and ruled the only part of the world that mattered.

At the top of the pedestal there is a twisted mass of ruined metal. Fragments weighing hundreds of pounds lie scattered across the floor for dozens of yards. The grey stone all around is riven with cracks and fissures.

In the center, where the throne once rested, a silver scimitar has broken the pedestal and stands there embedded. A thin layer of frost has accumulated along the blade despite the constant stale warmth of the Heartspire. Otherwise it is perfect, undulled and unmarred by time.

History records precisely one visit by Luna and Celestia to the Heartspire.

To reach the higher levels of the tower, one must take a bit of a detour. There are no ramps leading up from the throne room. Only unicorns capable of teleporting can go any higher.

The walls are noticeably closer now, dozens instead of hundreds of yards apart. Unicorns who teleported directly to this level from the ground felt their ears pop, and sometimes they grew breathless and faint if they moved too quickly. It was a small price to pay for being closer to the stars.

The level has the feel of a ritual space. Marble basins filled with dust line the walls, and the stones are filled with elaborate carvings. Legions of ponies march in relief across the walls; earth ponies haul stone blocks across a featureless field broken only by the image of a low, incomplete tower. Unicorns stand among them, passing out food and drink, and using their magic to aid the earth ponies in placing the blocks.

The images are different on the next level.

The earth ponies are smaller, their features crude and animalistic. The sculptor has not bothered to give them cutie marks.

The unicorns no longer stand among them. They oversee them from raised platforms. Their features are refined and detailed, with complex armor and cutie marks. The sculptor has carved individual strands of hair in their manes.

The tower in the distance is higher.

There are no earth ponies on the next level. Heroic unicorns march across the walls, far larger than the real ponies who once stood here. Beneath their hooves, fading away into the background, the sculptor has etched what may be a sea of backs and manes and tails, toiling in obscurity. They bear up their highborn lords.

In the distance, the Heartspire stands tall and complete. The sculptor has carved rays like the sun's shining from its peak.

Part of the wall is damaged. Through a small gap barely larger than a pony’s head, the world stretches away to the distant, curved horizon. Clouds drift below the impromptu window.

For the first time, a scent other than dirt and stone fills the air. It drifts in from the opening.

It is ash.

The highest level is largely missing.

Only a few square yards of the floor remain. Some tremendous, violent force has opened the room to the sky, and half the walls are simply gone. The ceiling and spire above -- hundreds of tons of granite-- sway in time with the wind. Only the tower’s residual magic keeps the entire affair from collapsing.

A stone altar slumps in the center of the room. It has melted like a candle left too near a fire, and rivulets of solid rock flow across the floor. Its black, charred surface is speckled with bright points where crystals formed when minerals in the stone began to fuse.

The surviving walls are blackened, but they still tell a story. Rows of unicorns bear earth ponies in the air above them, carrying them up spiraling ramps, higher and higher, past gardens and homes and a throne and basins flowing with water. Higher and higher the unicorns bear their captives, until they reach a room with a stone altar.

The rest of the story is lost, along with the walls in which it was carved. Only the Heartspire’s ghosts know the rest.

Along with Celestia and Luna, who visited the Heartspire but once.