The gateway to Islam's holiest city features a huge structure arching over the road, marking Mecca's boundary in an otherwise empty desert. The archway at Mecca, shaped like a large book propped open, represents Islam's holy scripture, the Koran. From this point on, only Muslims may enter. In practice, it's truly a miracle. It flows quite smoothly despite the congested mass of fatigued travelers.
People manage to get from place to place.
They even manage to perform their prayers, ablutions and rituals relatively safely. There have been some deaths from crushes in the past, but these have occurred near the tent city at Mina, outside Mecca, due to particular circumstances specific to that location. The Hajj Research Centre studies the logistics of the Hajj closely every year, looking to improve safety and comfort. Billions of dollars have been spent by the Saudi government to expand the already-huge Great Mosque in Mecca. It can now house more than 1 million people for prayers, but worshippers still overflow into the streets as far as a kilometre from the doors of the structure.