Llanberis RAF Reserve Depot was a munitions store located at FFord Clegir, Llanberis, Caernarvonshire.
It was opened at the outbreak of World War II for the storage of up to 18,000 tons of bombs for the RAF. However, in January 1942 much of the structure collapsed burying almost 14,000 tons of bombs. Although most of the stock was recovered, it brought the end of underground storage there.
The site was still used for the storage of incendiaries and other material. The demolition and burning of explosives within the quarry area started in June 1943 when the Royal Air Force School of Explosives moved to the site. The destruction of explosives continued until July 1956 when the site was closed.
However the problem of unexploded ordnance proved a major problem and in 1969 a decision was taken to clear the entire site of explosives and explosive debris. In 1973 the lake was drained to reveal that the bed of the lake was littered with explosive items including a number of large bombs. It took another two years to clear this.