[Jimjam]

Hey guys, I know plenty of you are rugged individualists and amateur historians.

I need your help!

After years of mowing the lawn and not feeding it properly, thereby scalping away the earth, some rocky surfaces started to protrude from the grass.

This was made all the more apparent after some building work, which more or less did in most of the grass.

Revealed, was the top of a structure square in shape, roughly 4ft by 4 ft and filled with earth.

Within the bounds of the walls the ground was particularly damp - as if it didn't properly drain.

I figured, perhaps it was the hard border to an old flower bed. I could dig it out and re-lay it for better drainage.

So I got out my (t)rusty spade and started digging. It turned out these 'borders' were actually walls, made of bricks larger than a standard red brick but smaller than a breezeblock. I kept digging my trench down, to about 3 or 4 feet, and hit water.

At first I was worried I had breached a pipe - but there was no pressure behind the flood, and it was odourless - so I think it is unlikely to be a pipe - neither supply nor waste. I was able to bail out most of the water and the flood didn't refill. I think it may be standing water from rain and snow which was unable to drain.

Due to the depth of the structure, I no longer think it is an old flower bed. It was mostly filled with earth, and a couple of bricks, some terra cotta and a relatively small slab of concrete or two. Not much rubble for the size of it. I also found the blade of a knife, and some hard, brown metal rods - about 3 inches in length - with bulbous ends and something green about an inch or two in length with 3 fins, shaped a bit like the end of a torpedo.

Any idea what these walls may (or the contents) have been? A pond? some kind of pen? A small bomb shelter (the garden is in a UK city)? There was no surface structure - just some underground walls.