Redcliffe, Bristol 2002
Over a fence and behind a derelict building; this doorway had a hole just big enough to squeeze through.
The hole led to a labyrinth of tunnels and chambers carved out of red sandstone, known as Redcliffe Caves.
After finding the entrance, I went back one night, armed with a torch and an accomplice.
We had to sample several pints of cider in the nearby pub before we stumbled over towards the doorway.  Over a wall, a fence, then ground strewn with bottles and rubbish, before we got to the entrance. Torches out and ready to enter. But this time no hole.
Someone had filled the wall with concrete blocks.
Disappointed, we headed back to the pub for more cider.

The caves are locked but visits can be arranged through Bristol Tours, they are also open to visitors on Bristol Doors open day and are well worth a visit.