3D overview of the tunnel system


Piecing together the evidence

The only measurements and angles we have were undertaken in the 1960s by two amateurs, Paget and Jones. Over a period of several years they refined these as best they could, working in extremely confined and hostile conditions, in tunnels almost completely blocked in many places by tons of soil brought in by the Romans.

Collating enough information to attempt a 3D computer reconstruction has been problematic. Paget wrote two descriptions of the tunnel complex. One set of data is in his book ‘In the Footsteps of Orpheus’, the other is in a paper he wrote for the British School at Rome. In the latter he gives no details of the exterior buildings at all. The book has measurements in imperial feet and inches whereas the paper has measurements in metric metres. In some details they don’t quite match. In some of Paget’s drawings, executed by a friend, there seem to be mistakes, probably due to interpretation.

Key features

In total there are some 350 metres (1,148 feet) of narrow tunnels which we know about. There are likely to be more features yet undiscovered.

The tunnels descent to a depth of 50 metres (164 feet) from the crest of the hill, with the lowest part being the fresh water River Styx, sitting just a few metres above sea level.

The whole complex of tunnels was lit by more than 500 lamps, the niches for which can be seen in the walls. The imprints of the lamps themselves and the oils stains down the walls can still be seen. These lamps point to a ceremonial use – it would be far easier for a person to carry his own torch in there than to light 500 lamps.

There are S bends at two strategic places, their only purpose would seem to be to obscure the view of what lies ahead. One S bend hides a two-way door. The other S bend hides the plartform at the start of the River Styx.

There is a vaulted sanctuary area which has been partially blocked by Roman masonry to allow an access corridor around two of its sides. The interior of this sanctuary has been filled almost to the roof with soil and has not yet been explored, although Jones did climb part way onto the top top of the settled soil and shone a torch into it. Parts of it were obscured to his view, so we cannot know exactly what is inside, how far it extends or whether there are any other tunnels leading off it.

Paget’s plan

The plan shown here is from Paget’s paper to the British School at Rome. There are two obvious mistakes on it.

The first is that the two D-shaped baths that are on two sides of the forecourt in front of the Painted Room are shown here tacked onto the side of the Painted Room itself.

The second mistake is that the scale is wrong when compared to figures given in the text.

As you can see from Paget’s sketch, he has named a number of the features within the hill.

The naming of the tunnels has been taken from their compass bearings. Thus the main entrance tunnel going west is called 270.

In my own reconstruction I will stick to the naming convention used by Paget and Jones, although I add a º, degree symbol, to my drawings to make it clear they refer to compass orientations.

My reconstruction

Any reconstruction of mine is almost bound to be wrong in places, especially where we only have a written description to go on, but the general layout will be reasonably true and accurate. I must emphasise that no archaeological survey has ever been undertaken.

More detailed areas will be discussed on their own pages.

General overview

A bird’s eye view from above. If we could look into the ground below and behind the cliff face, we would see that there are a collection of features, immediately behind the set of five visible surface buildings.

The shadow in the picture below represents sea level. The conventional explanation of the entrance tunnel is that it is merely a channel to supply hot water and steam to the Roman baths. As we can see, the passage descends, so that any water flow would go into the hill, not out of it.

2 Responses to 3D overview of the tunnel system
  1. Victor Reijs Reply

    John what is the angle of the tunnel’s incline? Is it around 1.5 degrees? The altitude of the skyline is around 1.35 deg, so close indeed.

    • antrum Reply

      I am not sure Victor. The drop down the Great Antrum to the divide is a very shallow and gentle descent until the Divide, at which point one is aware of a quite dramatic drop. Doc Paget mentioned the distance down at the 425 foot mark, but this would need to be confirmed by more modern surveying. We can get this investigated. I will check what Paget said.

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