Saturday, 19 March 2011

semi-urban exploration: Llanberis RAF Reserve depot (bomb store)

At a bit of a loose end yesterday following a Lyon Equipment course at Plas-y-Brenin, I found myself sat in Pete’s Eats with a cup of tea and a plate of eggs on toast, wondering what to do with the day. I quite fancied a hillwalk, but somehow couldn’t motivate myself toward anything I’d already done before, and couldn’t head anywhere new because I was somewhat lacking in the map department. I texted a couple of people, and my friend Sion headed over and met me in the cafe. After a little discussion the decision was made to go and check out the old bomb store just outside Llanberis town – now, I should just say that this place is somewhere I’d been meaning to go for a while, and so, being with someone who knew [roughly] where it was and how to get in, I was keen to head over.

Equipped with Sion’s somewhat hazy idea of how to get to the place, and several torches that we cleverly left in the car, we headed in…or at least we thought we were heading in, until we realised that we in fact were not heading in to where we wanted to be, but to somewhere else. So we headed out again. After a little wandering and some cunning use of mobile technology (Google mapping and satellite views on my phone…damned impressive), we eventually found the right section of quarry and made our way down into the depot itself.

gallery view

We wandered around some of the old access tunnels, using only the torches built into our phones (as I mentioned earlier, the proper torches were being stored in the car for safe keeping at this point), and eventually popped out through a big steel door, essentially back next to the road. The decision to retrieve the torches was then made, after which we returned to explore the main stores themselves.

SDC12621  Sion donning his headtorch before entering the main chambers

The place is huge. Truly enormous, especially when you consider the large open concrete area through which the railway bed runs was actually once also completely covered over…

If, like me, you’re interested in the history of this place, head over to Subterranea Britannica and read their article, here.


The depot was built by the Air Ministry between 1939 and 1941 for the storage of around 18,000 tons of bombs. Rather unfortunately, a mere six months after the depot was opened it suffered a catastrophic failure, where some two thirds of the roof structure collapsed under the weight of its layer of slate backfill (due to 'cost cutting’ design changes). A train of twenty seven wagons, at the time in the process of unloading, was engulfed and around 14,000 tons of bombs were buried (which actually represented around 14% of the entire RAF stock).

The collapse signalled the end of the storage of bombs underground at Llanberis, although most of the buried ordnance was recovered. The depot did remain in use for open storage of incendiaries and demolition works, and was finally closed in 1956.

The site remained active militarily for several decades, with all explosives being removed between 1969 and October 1975, by 71 Maintenance Unit EOD Flight from Royal Air Force Bicester. (Incidentally, due to the nature of the site, and the multiple pit areas used for the dumping of explosives, this exercise was one of very few that have ever required military personnel to first be trained by a Mountain Rescue Team: the various rock climbing techniques and rescue procedures taught were essential to enable members of the unit to reach much of the explosive ordnance with which they had to deal.)

SDC12623 SDC12628





The site is a fascinating place, and one I’d have loved to have seen whilst it was operational. I really must do more exploring…


  1. That is so cool! Nice photographs, I really enjoy "bunker exploration" and we have some cool one here in Sweden as well.

    In fact our new radio core for the new train radio is being developed in one that SL has taken over from the civil defence part.

  2. Oh really? Need some pictures matey!