Watch: what happens to your luggage when you check in at an airport
Dubai is officially the world's busiest airport, seeing a record number of passengers in 2016.
More than 83 million passengers on 90 airlines flew into the skyscraper-studded hub last year, a gateway for East-West travel.
And with all those passengers comes even more bags. Just 25 metres beneath the airport lies a bizarre, subterranean world with a sprawling 129km high-speed railway network.
Costing more than $800 million to build, Dubai Airport has the world's biggest luggage system.
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"Everywhere you go, there are just miles and miles of these conveyor belts, of these carriages of suitcases moving along," City in the Sky's Dallas Campbell said on his tour of the airport.
"It's like some sort of post-apocolypic fairground ride."
The completely automated system doesn't require any human input, unless something breaks down, of course.
"It's like the robots have taken over," Dallas said.
So how does it work? Watch the video above to find out.
City in the Sky airs Tuesdays at 9.35pm on TVNZ 1.