One, two, three, four, five.

Count slowly, not too fast.

Mississippi six, Mississippi seven, Mississippi eight.

Seconds passing – then some more.

Nine, ten, eleven.

Stand absolutely still.

Twelve, thirteen, fourteen.

Feel the chill sink into your bones.

Fifteen, sixteen, seventeen.

Seventeen seconds.

That’s how long it takes the astonishing echo of my footfalls to fade, in the German Military Underground Hospital on the Channel Island of Guernsey.

It is a huge network of underground tunnels built under a hillside by the Germans during their occupation of Guernsey in the second world war.

It’s in the middle of the countryside, in a quiet rural spot, half way along a sleepy residential road.  Maybe in the summer it is teeming with tourist cars and coaches, but at the moment, on a dull day late in the year, I appear to be the only person here.

I have been dropped off by taxi and make my way along the path to the entrance in the hillside.  After a cheery greeting from a man who has a pretty lonely job, and paying for my entrance ticket, I am gestured onwards and asked to enjoy my visit.

The first thing I notice is the cold.  The second is the stillness.

And then, as I start to walk – the amazing echo.

It’s by chance that I have noisy shoes on, they might have been quieter ones – they are certainly flat and sensible, in anticipation of a day’s exploring.  As my heels click on the flat concrete floors, the noise is thrown into what is clearly a massive and cavernous space, reverberating astonishingly, unlike anything I have ever heard before.

Imagine the sound of walking through a deserted underground carpark.  Then multiply times ten.

As I wander on my own through the long tunnels and damp archways of this amazing warren of rooms and passageways, I can hear somewhere in the distance the footsteps and murmurings of other visitors.  It transpires that there is one other couple in the hospital whilst I explore.  I see them occasionally in the distance, and hearing them provides a small comfort and reference point.  But after a while I hear a door slam, a long way away, and after the noise of it has been amplified by the underground architecture and then gradually faded to silence, I realise that I am now entirely alone.

These tunnels were hewn out of solid rock by slave labour.  Several of the workers died during its construction.  This place was only ever used for a few months as a hospital, and ended up being used as an ammunition store.

There are a few museum pieces of furniture and equipment around, but mostly the long, dark wards and corridors are wet and empty.

I walk and walk, absorbing the atmosphere, imagining myself having to sleep down here – bad enough for one night, horrendous over weeks or months.  I stand for long minutes in a dimly lit ward, taking in the absolute stillness, the forgotten isolation of the place.

I experience utter seclusion.

I battle with innate fear.  I know I am safe, there is a man on the door, I would hear anyone else coming.  But what of ghosts?  Imagine I saw something move suddenly?  One of the rooms is – was – a morgue.  I stand in it ghoulishly, feeling for spirits, challenging them almost to show themselves to me.

I can feel the echo of the fear I might feel, should such a thing suddenly in fact happen to me!

More realistically, I worry about a power cut and the lights fading.  That would be a cause for panic, and a bad experience certainly.  But the lonely man at the door knows I am here, he would come and get me with a torch, surely?

In some areas there is water dripping like in a natural cave.  In places there are long ladders reaching upwards, through emergency escape shafts dating from those times.  I imagine the horror of trying to climb one.

I walk some more – the extent of the place is amazing, seemingly endless.  I think to myself that, though I have been in several caves and caverns, and even other man-made tunnels, on my various travels, I have never experienced anywhere with quite such an atmosphere as this.

And above all – the most memorable thing – is that incredible acoustic.  I clap my hands and imagine the sound waves rushing into all the forks of the tunnels, through all the rooms, spreading out into the warren of still air, making it ring.

And it’s not just the length of the echo that is striking – it’s the quality!  It creates such a full, rich, cumulative sound.  Of course there is no-where for the sound to escape, it’s a completely enclosed space.  The sound is trapped, it ricochets off all the walls, repeating and interacting with itself.

Convinced now from the absence of sound that there are no other visitors in the place other than myself, I cannot resist singing a chord as I have sometimes done in cathedrals, to create an organ effect.

Careful to be in tune, I sing an arpeggio of notes, in quick, distinct bursts.  More than an octave, I sing, to get a fuller effect.  First a major chord, then once the air is still again, a minor.

The effect is pleasing.  I hope the ghosts are enjoying my little concert.

Later, when I exit back into the leafy outdoors, I comment on the acoustics and am told that a boys’ choir has recently performed in the hospital, especially to make the most of that spectacular sound phenomenon.

I find myself wondering also at the awful cacophony of noise that must have been created by the people actually living down here, all those years ago.  Soldiers’ boots stomping about, doctors and nurses talking, patients crying out, equipment clattering – heavens, it would have been deafening!

I head for the exit, eventually, counting the length of the stupendous echo a few more times, certain I’ll never experience a bigger or longer one again.

I think of that place sometimes – think of it as it was in the war, or as it is now, in the middle of the night perhaps, absolutely still and dark.

A silent, obscene folly, transformed once by my shoes and my voice into a spooky echo chamber, waiting in vain stillness for my return.