Among those millions was a group of students from Hong Kong: the 54 winners of the Young Post-CMA Green Manufacturing Competition which ran earlier this year visited the Expo on October 17 and 18.
As we drove from the airport to our first Shanghainese meal, students oohed and aahed at the city's skyline, certain that, if the city was this impressive, the Expo was sure to take their breath away.
We arrived before 10am but the crowds had already started to gather at the gates. This was hardly surprising - we'd heard that more than a million people had visited the day before.
The queues were everything you've heard about - and more. After getting off our coach, we queued for a bus which drove us to the gates. We then queued to go through security - even at 10am there were thousands of people waiting to get in, chatting excitedly as they caught a tantalising glimpse of the pavilions.
And when we eventually got in, what a sight met our eyes. Towering buildings in all colours, shapes and sizes, housing exhibits from nearly every country. And more queues. Regular announcements inform you how long you'll wait in certain queues so that you can plan your day. With predicted waits of up to five hours for some pavilions, including Saudi Arabia and Britain, it was no wonder people were eager to visit less famous pavilions such as Moldova and Bahrain.
We headed to the Hong Kong pavilion, which is sponsored by the CMA. The metallic structure lies in the shadow of the majestic China pavilion, and next to the quirky, rabbit-lantern-shaped Macau pavilion. The design incorporates typical Hong Kong items such as the red "egg-checking" lamps and photo-sticker-style photo booths. After watching a short 3D video about the city, visitors enter a room of interactive screens to learn more about Hong Kong's financial prowess, before finishing in the Mai Po-inspired roof garden.
While the students were proud that their city's countryside had been represented, several of them expressed disappointment that there wasn't more focus on the city's creative industries.
If we thought we'd spent too long waiting so far, we had no idea. We went to the China pavilion, a spectacular red structure inspired by traditional dougong, or brackets. The queues were less impressive - around four hours - but most of us felt it was worth it.
Inside, visitors are treated to a range of exhibits, such as a video depicting China's development over the past four decades and a funfair-style ride illustrating the challenges of urbanisation.
Perhaps the pavilion - and the Expo - is best summed up in the words of Suki Leung Shuk-in, from City University: "A combination of our traditional culture and modern technology, which shows our brilliant future while preserving the good old things."