What is so special about Gopuram (tower) in Hindu temples? - a brief note

Hindu temple plan. pinterest.com

Above image: The plan of a Hindu temple is based on the human body in a lying posture. The feet represent the entrance to the temple. Flag-staff represents the center of the human body. Sanctum  and adjacent mandaps (halls) represent the head, and chest and abdomen respectively......................................... 
Basic temple parts. godsownweb.blogspot.com

Above image: Entrance gopuram is taller than the tower (vimana) above the sanctum (garbagriha). Namaskara mandaba is just away from the sanctum where devotees prostrate before the deity. Many people believe it should be done in a spot on the right side of flag-staff (Dwajasthambam). After doing prayer in the sanctum, the devotee should go round the temple clock-wise. The number of Prathakshna should be in odd number preferably 3 and 9. Prostration of a Hindu devotee in the temple is symbolic of surrender to the Almighty...................................

Though the Indian temples are built in a pattern native to a particular region, the structure of Hindu temples is based on 4 collective principles  of human life : they are  Artha (wealth, prosperity), Kama (pleasure, sex), Dharma (ethics, values), Moksha (self-realization, freedom from life or reaching heaven!). In this transient world, we must do our duty correctly as we progress in age. Self-contentment promotes happiness and peace of mind.
Sketch of gopura. en.wikipedia.org
Above image:  The gopuram in the picture has single story. A gopura is an entrance gate, usually ornate with odd number of kalasa on top. It may have one or many stories. Even the stories  are in odd number...... 

Big temples normally have four towers - entrance gates at coordinal direction; ordinal directions are not allowed; small ones have a single gopura above the entrance gate. In the medieval temples the gopurams/towers appeared to be small. but in the later period they became  prominent feature of Hindu Dravidian style. During the rule Pandya, Nayaka and Vijayanagara, temples became centers of activities for the people and the gateway towers with fine decorations and sculptures   became taller and prominent part of the sky line of the towns and villages. The massive towers and inner courtyards obstructed the view of the inner sanctuary of the temples. When the upwardly tapering tower is  divided into many stores (talas), it decreases in size successively as the gopuram tower narrows at top.. Usually the tower is topped with a barrel vaulted roof with a finial. This type of style appeared in the 10th and 11th centuries CE. Example: the shore temple of  Mahabalipuram  and Thanjavur big temple. temples with multi towers (gopurams) started evolving in the 11th century on ward. The 4 tower Chidambaram Nataraja temple appeared  in the 13th century and completed in the later period.

 Among the parts of a Hindu temple, regardless of style or architecture, be it Dravidian or Nagara,  Vimana forms an important part. This structure  over the inner sanctum/garbhagriha is common among  the Hindu temples of North India and Odisha in East India. The main garbhagriha is the place (in Tamil Karuvarai) where the presiding deity is enshrined.  Temple Gopuram through which we get into the temple enclosure, it is believed.  represents the feet of the divinity and the sanctum / garbhagriha represents the sirasu -head of divinity. A devotee bows at the feet of the Lord at the  gate as he steps into the temple  with humility and proceeds toward the chamber or inner sanctuary  to surrender to him, leaving behind the  mundane world of  confusion, commotion and contradiction. He is there to be at peace with himself in the sanctified place of worship right before the deity where the positive energy flows.  There is a well known saying in Tamil: "Gopura Darshanam Koti Paapa Nashanam" meaning  the darshan of a temple gopuram will get rid of  10 million sins. Hence, temple towers/ gopurams are  sacred to the Hindus.........
Hindu temple, northern and southern styles.  templepurohit.com

Above image: Dravidian temple design:  The temples have  pyramid shaped towers and are made of soapstone, sandstone or granite, depending on the availability of rocks. In karnataka soapstone rocks are available in plenty, whereas in Tamil Nadu granite and granite related rocks are available in plenty. The principle part of the temple - Vimana,  is  square in plan surmounted by a pyramidal structure. The most pertinent part inside the temple is called the Mandapa (s) (halls)..........................

North Indian temple design:   They have a square garbhagriha - sanctum  with adjacent pillared mandapas (halls or porches) that are connected  to the sanctum by a vestibule (antaralas). Unlike  south Indian temples, the ones in the north have embellished entrance to the sanctum  with figures of  deities and geometric ornamentation. The temples usually contain a shrine and a  meditation hall to engage in silent prayer and meditation. They  are   basically squares with several gradual projections in the center of each side. This gives  a cruciform shape with a number of re-entrant angles on each sides .

Normally, a gopura is built  with an enormous stone base in a rectangular plan  and a superstructure of brick  above it with support. It is topped by a barrel-vault roof crowned with a row of finials.  Height, size, etc differ from temples to temples. But the main plan of the temple  is the same.  It is quite interesting to note that the height of Vimana over the inner sanctum is not uniform across India. Among the temples of East India  where Kalinga style of architecture is predominant, the Vimana is the tallest structure. This is also true of north and West India where the tower with Vimana rises to a great height above the sanctum. On the contrary, in most of the south Indian temples, the Vimana over the inner sanctum is very much shorter than the entrance gate  tower or towers (gopuras)  on all four sides - East, west, north and south. With exceptions, this is a typical Dravidian style of temple architecture. 

The terminology also differs as in the case of the superstructure over the garbhagriha, it is referred to as a 'shikhara'. But, as far as south Indian temple architecture is concerned, the term shikhara means a dome-shaped crowning cap above the Vimana. Among the entrance gate towers -gopura at four directions on the outer most walls, the East one is the main entrance to the temple. Rest of the gateways under the gopura are opened on certain auspicious days. The belief has been that if you choose one of these gate ways, you are assured of salvation, a place in heaven (Swargham) - meaning no rebirth will haunt you. 

The tower/ vimana  over the inner sanctum  does not get as much importance as the entrance gate towers on the outer walls. In a few temples the roof of the sanctum assumes much importance regardless of its size, shape and height.

tower above the sanctum, Thanjavur big temple.trekearth.com
  In the case of the world famous UNESCO recognized heritage site - Brihadeeshwara temple of Thanjavur, TN, the inner sanctum where lord Shiva is enshrined in the form of a giant lingam, has a granite stone tower above it -  216 feet tall and perhaps the tallest tower -vimana above the sanctum in India. A tall gopuram or tower  right above the  inner most sanctuary Sri kovil is a rare one in the Dravidian or Tamizhagam  Hindu temple architecture............................

Tallest  Main Tower in India, Srirangam Ranganathar temple,TN

Srirangam temple. small gold-plated tower above the sanctum shtadevata.com
At Sri Ranganather temple of Srirangam,TN  above the main sanctum where lord Vishnu is worshiped with his consorts, the gold plated vimana is a small one. 

The gold plated above sanctum. note the tall tentrance tower

At Tirupati Venkateswara temple the Ananda Nilayam, the gopuram of the main shrine occupies a very special place in the temple's history and identity. So is the gold plated small vimana above the sanctum.

Golden roof above sanctum, Chidambaram Nataraja temple.tripadvisor.com

At the famous  Sri Nataraja  temple, Chidambaram, TN the garbagriha assumes a different configuration.   The roof of  the kanaka-sabai (Golden Stage) here is entirely covered with  thick golden plates.  King Parantaka I funded to cover this vimana with ornamental gold and it retains its glory even today; the structure being  massive in size not in terms of height, when compared to most other vimanas.
Madurai Meenakshi temple. tall entrance towers above sanctum  small tower.
At Madurai Meenakshi Amman temple there are two sanctums one for  lord Sundareswarar (Shiva) and another for Parvati (Meenakshi). Both vimanas over the sanctum are small and gold plated. Whereas the entrance towers facing all the four coordinal directions are tall ones and can be seen from considerable distance...................................
Puri Jagannath temple, odisha tower above sanctum commons.wikimedia.org
At the famous Jagannath Temple, Puri, there is  a huge  Neelachakra on the Amalala atop sikhara, i.e., the top of the Vimana. It is symbolic of   God Vishnu's most powerful weapon, the sudarshana chakra. The tower is above the sanctum.