TELLY historian Michael Scott plumbed the depths for his latest Invisible Cities series.
They take viewers to some of the lesser-known, hidden spaces of the ancient world, never filmed before because of the difficulties of access.
The latest series, Ancient Invisible Cities, goes deep underground beneath the pyramids in Cairo and into tunnels in Athens.
The latter really pushed Michael, who is based at Warwick University.
“It was so difficult that we needed an entire safety crew with us,” explained Michael, with the directors for the series based in Glasgow and the editing also done at the BBC’s Scottish HQ.
“We had to abseil 16 metres down a shaft to reach an underground tunnel which was so narrow that at one point I turned my head and my safety helmet got stuck.
“And at other points it was so low that all you could do was lie down in the water that still ran through this 2,000-year-old aqueduct and let it carry you along.
“The top of the tunnel was inches above your nose. I have slight claustrophobia and moments like that pushed me to the absolute limits of what I could do. Then the only way out at the end was to free climb back up the abseiling ropes.”
Michael insists that there were important lessons to be learned from getting to such inaccessible places. And as well as capturing them on film for the first time, he says the series will also have a lasting legacy.
“We had 3D laser scanners with us and used them to scan these tunnels and aqueducts. We not only use that in the programmes but we also turn them into virtual reality and people will be able to visit these 360 degree videos and experience something like we did.”
Ancient Invisible Cities, BBC 2, Friday 9pm.