This post from The Pop-Up City looks at the air conditioning unit that cools the tents used during the Hajj, and the bridges built for the masses of pedestrians.
"Maybe the most interesting construction in Mina is the Jamarat Bridge. It is built to facilitate the movement of worshippers arriving from various directions. The bridge has 24 access routes and 11 gates linking it to the mountains from all directions. Currently there is 5 levels of the bridge, which can be extended to 12 in the future."