The Guidebooks Stop At Eight Levels. Two Resistivity Lines Found Voids At 141 Metres.

DERINKUYU, Turkey — On 11 August two 420-metre resistivity lines were run across the streets of Derinkuyu. Both image continuous low-resistivity structure beginning at 96 metres — eleven metres below the deepest point in the published record — and continuing, on one of the two processings, to 141.

The published depth of the underground city is eighty-five metres.

That number comes from a water pipe.

Where eighty-five metres came from

The town archive holds the waterworks file for 1963 to 1971. It costs forty lira to copy and nobody asked us why we wanted it.

In 1965 a municipal trench for a new main was cut down the eastern side of the town and broke into the complex at three points. The trench log records its own floor at 85.0 metres and stops, because the pipe it was carrying stops.

Two years later a survey adopted that figure as the base of the excavated complex and added the phrase "no evidence of further development below". Both statements were true of what had been dug.

Neither was ever a statement about the rock. By about 1980 the distinction had gone, and the eighty-five metres had become the depth of the city — in the literature, on the interpretation boards, and in four stories in this newspaper's own archive.

What the lines show

Dr. Naciye Ergüven-Kaltenbach ran the survey and we sent her data to a second processor with the locations stripped off.

They agree down to 118 metres: continuous structure, responses spaced regularly to within 1.2 metres, of a kind neither of them would expect from dissolution alone.

Below 118 they split. Ergüven-Kaltenbach stands behind responses to the limit of the array at 141 metres. Dr. Solvej Aygün-Radich calls them a depth artefact and says she can make them appear or vanish by changing one inversion parameter, and she demonstrated this for us twice.

We are not going to settle that by picking the one we like.

The gallery

At 62 metres, on both lines, there is a linear low-resistivity feature 3.4 metres across, running on a bearing of 191 degrees and holding a gradient of 0.4 per cent.

We followed it with a third profile for 2.1 kilometres before the ground we could legally stand on ran out at a field boundary. On that bearing, Kaymaklı is 8.8 kilometres away.

Every guidebook in the province mentions the tunnel between the two cities and calls it a tradition. We are not claiming it arrives. We are reporting that something 3.4 metres wide leaves Derinkuyu heading south and does not deviate for two kilometres, which is not what water does.

The man who was fined

In 1994 Tahsin Örsel-Weber went through a collapse in a private cellar and came out below the closed gate.

He describes four chambers, the last of them large and dry, reached by a passage that turned twice. He kept a notebook, he has no photographs, and he was fined 2,400 lira.

His described position for the fourth chamber sits within twenty metres of our strongest anomaly. He gave us the position before he saw our lines. That is the single most persuasive thing in this story and it rests on one man's memory of one afternoon thirty-two years ago, which is why it is in the fourth section and not the first.

What this desk takes from it

There is more under this town than has ever been published, and the reason it was never published is not a ministry and not a committee.

It is a plumber's trench, a true sentence about it, and sixty years of people copying the sentence without going back to see what it was measuring.

The reason nobody has gone down since is better than that, and the site director sets it out below at greater length than we asked for. Thirty-four thousand people drink from those levels. A borehole into them is not an excavation, it is a water supply, and she is the one who would have to sign.

We would have liked a more interesting villain. We got a hydrogeology report. </content> </invoke>