I think it's really difficult to visit the whole site in just one day, especially if that day is a Satuday or Sunday when lots of people go. The main street (Decumano) doesn't look crowded because it's so wide and long but there can be long queues at the entrance of some pavilions like the Italian one and the Pavilion Zero.
Entrance was super fast, after the pedestrian bridge that connects the metro to the site, there were lots of people pointing the way, thorough security checks like at the airport and then you're in.
The first pavilion you see, if you come by train or metro is the Pavilion Zero, which I still have to visit because the queue to enter was long. From there you start walking thorugh the site along the Decumano and you'll find country pavilions on both sides, but also institutional pavilions, clusters, restaurants, bars and many other places you might want to stop and take a look at. Make sure to get a map from the many volunteeers.
There are art exhibits, wine bars like the Franciacorta corner, and a huge space for Eataly and its 20 regional Italian restaurants.The pavilions are huge, most of them also have restaurants or bars inside where you can buy typical food and drinks but beware of the prices, some of them are really high... but more on that in other posts, here are the photos of some of the pavilions I saw on my first visit:
First image (clockwise): Belgium; Nepal (still not open due to the tragedy of the earthquake - construction workers of other pavilions helped them finish the building); Vietnam; Sudan; Ireland; Rice cluster
Fourth image (clockwise): Kuwait; Ecuador; Germany; Slovenia; Iran; Switzerland.
Fifth image (clockwise): Colombia; China; Belarus; Argentina; Thailand; Malaysia.
Sixth image (clockwise): Spain, Vanke (Chinese company); Mexico; Kazakhstan; United Arab Emirates; United States of America.
Make sure you wear comfortable shoes!
To be continued...