My name is Rudiger Hess. In the mid-2000s, my partner Emiel Meijer and I led a U.N. team of excavators working on mass graves in the Balkans.

During our investigations, we relied heavily on records corroborated by witness testimony in locating graves.

It was a successful method, and we were largely able to locate and excavate the graves we knew existed and occasionally find ones unknown to the official sources.

One day, we accidentally identified a massacre site whose very existence our normally helpful witnesses refused to acknowledge or even speak about to such a degree that they crafted the most elaborate counter-explanations.

Naturally, this piqued our interest and despite the site being unconfirmed and therefore beyond the scope of our mission we proceeded to excavate.

We worked at night.

What we discovered was that under a shallow layer of buried corpses there existed a slab of concrete, and when we drilled through that concrete, we discovered an emptiness.

At first we believed it was a cave.

After some deliberation, of which the options were to forget the discovery and return to official work or investigate further, a vote returned a slim majority in favour of investigation.

As the leader, I was the first to be lowered into the emptiness.

What I found was remarkable.

For as I was lowered on a rope deeper and deeper, I found myself at the same time lifted into a city populated by humans such as ourselves but whom gravity affected conversely!

By way of illustration:

Imagine a tabletop on which someone has arranged a world of miniatures. Buildings, people. This is our world. Now imagine that on the underside of the same tabletop someone has arranged another but upside-down world of miniatures. Finally, imagine the tabletop contains a hole, through which a miniature from our world may fall upwards into the sky of the underside world and vice versa because to the underside world ours is the upside-down.

When first I entered the emptiness, the Undersiders stopped in the streets and pointed at me.

Drivers pulled over, pedestrians dropped groceries.

Inverted birds flew past.

And I gripped the rope tightly, knowing that to let go would mean forever falling into the atmosphere—or beyond.

The first Undersiders with whom I interacted were police, but my first true communication was with a Serbian-speaking ad hoc committee of technocrats.

I was "lying" on the ceiling of a boardroom in which they were seated.

When they gave their names, I recognized them as murder victims, some of whose bodies I myself had excavated.

"And your name?" they asked me.

I gave it, and after a twenty-minute recess they reconvened and told me I had been murdered years ago.

I inquired about the circumstances.

"You were killed with your family during a recent war. The perpetrator was caught, tried and executed under orders of a military tribunal."

"Who was the perpetrator?" I asked out of blind curiosity.

They checked their papers.

"Emiel Meijer."