The weeds were waist-high at the foot of the watchtower; the windows were smashed, the door rusted open.

The whitewash on the main building had weathered to beige and flaked away and exposed the crumbling brick beneath. Razor wire coiled haphazardly round the edge of the roof. Windows were missing panes of glass behind the bars; some had been bricked up and a few, in what must have been administrative rooms, seemed stuck open.

Paterai Sea Fortress is a sprawling sextant-shaped building arranged – as an estate agent would say – over four floors, including the basement. It was built as a cannon battery in 1840 on the orders of the Tsar to protect the shipping lanes to St Petersburg; later it was converted into barracks, and later still to a prison. But it was long ago abandoned and left to decay.

The main wing curves around the waterfront and looks out across Tallinn Bay. Two smaller wings extend from the rear and meet at a point and enclose a courtyard with standard Soviet exercise blocks, three metre squared, surrounded by walls too high to see over, open at the top, but covered with mesh. A gangway for the guards runs between them.

I had read that it was possible to arrange guided tours but instead just turned up and walked in. I doubt that I was supposed to, but the gate was open and the security guard never looked up.

There was an eerie silence in corridors which once must have echoed with the slamming of doors, the jangle of keys, the clunk of locks; sobs and screams, jeers and shouts, the thumps and squeaks of scuffles, running feet and the sickening thuds of batons swung with abandon.

The paint was bubbling from the walls, and each accretion from each regime was visible; the chequerboard floor tiles were half-hidden under dust. A ventilation duct had burst open and its panels hung limply from the ceiling.

The administrative rooms had the look of being ransacked, or cleared out in a hurry by ham-fisted soldiers.  Drawers left open, doors hanging off cupboards; chairs knocked over and never picked up, the contents of files strewn across desks and over the floor. Smashed typewriters, telephones and office bric-a-brac spilling out into the corridor.

The dusty shelves in what used to be the library were bare, except for a few rows of toppled booklets, stray pages from books and screwed up newspapers with the headlines of twenty-five years ago.

A few of the cells still had skeletal bunks squeezed in rows under vaulted ceilings – it was thirty to a cell in Soviet times. The rest were hauntingly empty, expect, perhaps, for a solitary chair and paint which had peeled from the walls in strips and covered the floor like autumn leaves.

There was nothing to stop me nosing about wherever I liked and I wandered, as if at a gallery, down each of the long, empty corridors, stepping through gates which used to seal off each section, peering into rooms never knowing what I would find inside, with only natural light spilling through windows and into the corridor through open doors, and occasionally being plunged into total darkness and having to use the torch on my phone.

One room was filled with old chairs, spewing out stuffing, upside down bunks, collapsing cupboards, more Soviet newspapers, leg braces, and the remains of a notice with a heading in Russian which my phone translated, nonsensically, as “what to do if grab”.

Another room had a sink in one corner, missing its taps and stained dark brown, and a squat toilet whose walls were papered with fading pictures torn from magazines of young women who might well be grandmothers now.

The tiles in one room of the old prison hospital were still gleaming white, but the grouting around them was filthy with age and neglect and the paint, as elsewhere, was peeling away in sheets and the damp was blackening the plaster beneath.

Operatory lights were still attached to the ceiling, angled at the frame of an operating table and a mottled dentist’s chair. There were big broken bottles, scattered syringes and a box marked ‘ТАБЛЕТКИ’ (pills), and cabinets and machines and tables and chairs which looked as if they belonged in a hospital bay; but there were, as well, discordant notes like a flat iron, a house brick and the rusting head of a pitchfork. It looked like conceptual art.

It occurred to me, when I was at the far end of the corridor on the top floor, that the security guard would be likely at some point – I had no idea when – to lock the front door, shut the gate and go home for the day. It occurred to me, too, that no one knew I was inside.

Perhaps I might hear the door shut; and perhaps I might be able to run to an open window, or wrestle one open, and shout down to the security guard; but, then, this was the security guard who never noticed me going in.

I hurried a little after that, down to the claustrophobic basement where one room was filled with old bicycle wheels – surreal, but I was conditioned to the surreal by then – and out into the courtyard, where I waded through weeds to the exercise blocks, then quickly up, down and along the other wings.

In a melancholy room lined with heating pipes, spotted with damp, and lit through a small, high window, there was a trapdoor in the floor and a rusted hole in the ceiling above it where a hook used to be. This, apparently, was where prisoners were hanged.

There was no way that I was going to risk spending the night among the ghosts of this bleak and silent monolith. I made for the exit and slipped out again. The security guard never looked up.

© Richard Senior 2016