Beneath the city centre of Nottingham, the soft Sherwood Sandstone allowed the digging of cellars, even with medieval technology. So in the last 1700 years more than 400 (450, 500, 800) caves where cut out from the sandstone. The number given divers very strongly, which may be a result of new discoveries during the last two decades. On the other hand, actually the whole city has cellars underground, and as many are somehow connected its pretty difficult to count them. They were used as storerooms, factories, pub cellars (Ye olde Trip to Jerusalem), dwelling houses or air raid shelter.
The soft sandstone was used for digging, since people lived at this place. The oldest sections of the caves date back to the 4th century. The caves were first mentioned in the 9th century, by a travelling monk, who came to this area and mentioned that people actually lived in cave houses. He named the area in his description Tigguo Cobauc, Welsh Anglo-Saxon for “the place of caves”. It seems people lived actually in cave houses until the 15th century, when it became at least rare. Then the caves were used for other purposes. Many were used as cesspits, to produce fertiliser and raw material for leather making.
The caves became quite important during World War II, they saved thousands of lives. 86 of the caves were opened and transformed into air raid shelters. The emergency headquarters for the Air Raid Precautions was located at Brewhouse Yard in the caves which are now the Museum Of Nottingham Life.
Since the 1980s the caves became more widely known and there were several attempts to restore them. The first venue was the Caves of Nottingham, which has been renamed City of Caves some years ago. This name is sometimes also used for the city, some call Nottingham is the "Cappadocia" of the British Isles.
Most of the caves are private property. Some of them were destroyed during several centuries of city development. After all they make the ground unstable and major building projects tend to fill the caves with concrete to create a stable basement. But some caves are protected and can be visited as tourist attractions.
The Chester Formation (formerly Nottingham Castle Sandstone) of the Sherwood Sandstone Group is from the Triassic (250-245 Ma). Sands and gravels were deposited in a northerly flowing braided river, in a thick sequence of interbedded sediments. The fluvial deposits were buried and then cemented by anhydrite, gypsum, dolomite, calcite and quartz which was precipitated from the groundwater. Later it was uplifted and subjected to weathering and erosion, which formed the escarpment and the castle rock. The sandstone is soft enough to be excavated by hand, but its joints and faults are widely spaced, so it is structurally very sound. The rock permits maximum unsupported roof spans of up to 5 m.
Archaeologists are exploring the caves for decades now, and the Nottingham Caves Survey started a project to do a 3D laser-scan of the caves. The official database contains 850 entries, so thats