Wilting in the summer sun, tourists wait to climb Notre-Dame Cathedral and meet its gargoyles.

Four metres (13 feet) beneath them, a team of archaeologists is digging the other way – straight down and back in time, to Roman Paris nearly 2,000 years ago.

In 2019, fire brought Notre-Dame’s spire crashing down as the world watched. The cathedral was rebuilt and reopened in late 2024, and now Paris wants to soften the hot, bare square in front of it with trees and shade.

But in a city this old, the soil cannot be turned until what lies beneath it is excavated, in case it is damaged during the works.

So a slice of Notre-Dame’s forecourt has become an excavation site – an open pit ringed by barriers and crossed by a wooden walkway, a few steps from the queue.

French media have dubbed it the “dig of the century”.

“It’s a rare opportunity for us to work on something that’s tangibly going to make a difference to the history of Paris,” says Lucie Altenburg, a conservator with the Paris archaeology unit.