Rath Yatra is a Hindu pilgrimage.
On the second day of the brilliant (waxing) half of the
lunar month of Ashadh (June–July), the festival takes place.
Jagannath, a version of the god Krishna, is the main deity
worshipped at this festival.
This festival is celebrated across India, but particularly
at Puri, where the main temple of Jagannath is located.
Jagannath, his brother Balabhadra, and his sister Subhadra
are taken in procession from Puri's main street to another temple approximately
a mile distant during the festival.
They spend a week at this adjacent shrine before returning
to the Jagannath temple.
Devotees (bhakta) process the deities in three gigantic
wooden chariots (rath), which the devotees pull with long ropes.
The tallest of the three, Jagannath's, is forty-five feet
tall, thirty-five feet wide, and rolls on sixteen seven-foot-high wheels.
The English term "juggernaut" is a corruption of
Jagannath, and the idea of a juggernaut as an unstoppable force comes from the
velocity that these carts gained once they started moving.
One of the most popular legends in British colonial history
has Jagannath's enraged disciples committing suicide by putting themselves
beneath the car's wheels in order to die in front of God.
Despite the fact that such stories were widely circulated,
suicides of this kind were exceedingly rare.
Even still, pushing the carts posed a danger, since those
who lost their footing in the throng would be unable to stand up and may be
crushed by the wheels.
T. N. Madan (ed. ), Religion in India, 1991, is a good
source of knowledge.
You may also want to read more about Hinduism here.
Be sure to check out my writings on religion here.