Tiruvarur Azhi Ther May 2018, a great ratha event next only to Puri Jagannath of Odisha

Almost all popular temples of Tamil Nadu, in particular, conduct annual car festival which is part of Hindu temple worship.  Such temple cars /thers (chariots)  carry  representations of Hindu gods in the respective temples. The cars are usually used on annual festival days called 'Ther Thiruvizha' in Tamil witnessed by devotees in thousands. 
The Angelo-Indian word Juggernaut has its origin in India  derived from the largest size of the  temple car from Puri Jagannath, implying a tremendous, virtually unstoppable force or phenomenon.
The temple car festival of Tiruvarur is steeped in history,  so are this ancient  temple and the Azhi Ther. In the Delta districts of Tamil Nadu, Tiruvarur Ratha festival is an important ancient temple festival event and attracts the largest crowd next only to Puri Rath Yatra of Odisha
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The temple town of Tiruvarur, Tamil Nadu is synonymous with the famous Hindu temple dedicated to Thygaraja Swamy (lord Shiva), the largest temple water tank in India - Kamalayam and most importantly the huge temple chariot locally called Azhi Ther meaning a car like a deep ocean (Azhi refers to ocean in Tamil.“Azhisoozh Ulagu” meaning earth surrounded by ocean, “Azhiperalai” ie tsunami etc). The chariot festival is held annually either in the month of April or May  and  this year the Azhi Ther fete was celebrated on 27 May 2018 with bhakti and religious fervor. It is part of Panguni Uthiram festivities.  Lakhs of people make a beeline to this town to witness this colorful and exciting festival that has been around for centuries. 
This temple chariot - Ther is the biggest in Tamil Nadu, perhaps largest of its kind world-wide, 
Tiruvarur Azhi Ther (temple chariot). The Hindu
weighing roughly 400 tons, standing up to a height of 96 feet including the canopy. The wooden base - platform is about 36 feet tall from the ground with giant wheels and has a width of about 31 feet and is intricately carved, depicting scenes from the great Hindu epics and carrying images of gods and demi-gods. The wooden base alone weighs about 220 tons, the canopy over it additional decorative items, bamboo sticks, etc., add extra  weight. The total weight will be around 400, depending on the decorations used.

Normally processional deity  will arrive at the Devasiriya Mandapam  two weeks before following which the decoration of the magnificent chariot will commence. This year after flag-hoisting on the temple premises, urchavar arrived at the Devasiriya mandapam on 4 May. On the Chariot festival  day the deity will be ceremoniously placed on the altar of the chariot and special pujas will be performed for the deities.
Indian special postal cover Azhi ther. Tiruvarur) coins and more
 The Urchavar - procession idol of Thyagaraja swami and his consort Kondi/Parvati  -the divine couple will come out of the massive temple and bless the devotees who come to their abode year-round to get their blessings. The temple car will be pulled by a thousand people holding the huge, long rope locally called ther vadam. Besides, heavy-duty bulldozers will push the car from behind to produce extra thrust to make it easier for the devotees to get  the car moving. The chariot will move clockwise down the four Mada street around the temple with the devotees' chant Aroora Thyagesa renting the air. Pandits will be chanting mantras all along the route. . The temple car normally will start around 6 to 7 am in the morning and will get back to the base camp by late afternoon. Besides, the Azhi Ther there will be four more temple cars for the other deities in the procession. - Lord's consort Kamalambiga, Lord Ganesa, lord Subramanya and lord  Chandikeswarar. The great Saivite Tamil saints Appar, Sundarar and Thirugana samandar made a mention about this temple festival and Azhi ther in the Tamil devotional hymns composed by them. The festival will last for 25 days and the entire temple complex  and town will wear a festive look with devotees in thousands thronging the temple to be blessed by the almighty.

In so far as Azhi ther is concerned, though it has been around for centuries, it is not  celebrated as a continuous temple event for various reasons. The temple car festival was held in 2010  after a long gap of 20 long years. Thanks to ex CM of Tamil Nadu M. Karunanidhi, DMK chief and Tiruvarur MLA (his native place is Tirukuvalai, close to Tiruvarur) who put in serious efforts to revive the age-old car festival tradition at the temple. In 2016, the same car festival was held after a gap of six years as it took a while to completely renovate it. On the festival day when there is a sea of humanity descendin on the streets of Tiruvarur,  security is a problem and normally more than 1,000 police personnel  will be deployed to take care of the security arrangements.
https://navrangindia.blogspot.in/2016/07/thiruvarur-azhi-ther-big-ratha-tamil.html
https://en.wikipedia.org/wiki/Tiruvarur_Chariot_festival