
North-South Line: The construction of Amsterdam's underground North-South metro line was a tricky business as it burrowed beneath the foundations of old buildings and the city's waterways.

Deep in the past: Archaeologists worked in pressurized concrete chambers known as caissons to sift through soft dirt for hidden artifacts.

Years and years: The archaeologists unearthed around 700,000 artifacts ranging from mollusc shells thought to be 115,000 years old, right through to vintage cell phones.

Big project, big headaches: Difficulties involved in the North-South line's construction mean it took 15 years to build and cost way over its expected budget.

Extraordinary excavations: "The sheer mass of material we unearthed during the construction of the North-South line was extraordinary," says Peter Kranendonk, one of two senior archaeologists leading the excavations during the metro project.

Late service: The North-South line was inaugurated in July 2018, nearly seven years behind schedule. The route is six miles long -- of which 4.5 miles are underground.

Station museum: Rokin station, in the center of the North-South line, now doubles as a museum, displaying 10,000 artifacts dug up during the construction.

Heart of Amsterdam: Rokin lies right in the center of Amsterdam's concentric network of canals.