Brihadeeswara Temple of Thanjavur, Tamil Nadu: The hollow tower above the sanctum is the key design element to reduce overburden

 

   Brihadeeswara Temple,Thanjavur, collectingmoments.in

The 1010-year-old Brihadeeswara Temple in Thanjavur, Tamil Nadu,  a UNESCO World Heritage Site built by Rajaraja Chola I is . dedicated to God Shiva (as a massive 8.7 m lingam). The temple entirely made of hard rocks - granite and granite related rocks of Pre-cambrian age is an architectural marvel and is often called the Dakshina Meru.

Big temple Nandi facing the shrinecollecting
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Big temple, 2-story tall sanctum  dreamstime.com 

.   Hollow space above the sanctum, Big temple quora.com


Brihadeeswara Temple in Thanjavur TN slideshare.netin

Above image The Popular 1010-year-old Brihadeeswara Temple of Thanjavur, Tamil Nadu made entirely og hard rock in the Cauvery Delta region. A unique sanctum spanning more than to showcase the tall monolith huge Shiva Lingam. present above it is the shrinking hollow space forming the axis between the center of Cupola at top and the center point of the Lingam .........

Unlike typical Dravidian temples, its sanctum (garbhagriha) and the tower (sri-vimana) form a single vertical unit rising 13 stories to a height of 216 feet, topped by a 60-ton granite block and a 20-ton cupola-shaped sikhara. The garbhagriha covering 2 stories  features no window, a rare hollow tower right  above  the primary deity enshrined -  one of India’s largest monolithic  lingams, spanning two floors. One can see the hollow space of the tower (gopuram) up to a much higher level from the bottom. of the sanctum. 

The center point of the linga and the center point of the cupola atop the tower lie in the same vertical axis.   The garbhagriha is square in plan and is set  on a plinth. This is molded and 0.5 meters (1 ft 8 in) thick. It consists of upa pitham and adhishtanam, respectively 140 cm and 360 cm thick.

 In most of the temples you can not see the shikara  above the sanctum from inside; normally is a solid structure. Examples: Srirangam  Ranganathar temple, Madurai Meenakshi Amman  temple, etc where the towers the periphery are tall.

Hall close inner boundary walls

Above image: Thanjavur, TN Big Temple. Covered halls close to the inner boundary wall. There  are  countless lingams abutting the boundary walls in the  the inner halls. dreamstime.com 
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But, at Brihadeeswara temple, the sri-vimana rises  up to 13 floors (total height from the ground is 216 feet).and the uncovered prathkshana path goes  around the entire structure comprising the sanctum, 2  halls on the east side, etc.
 
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The vertically shrinking squares tower architecture of this temple is a  unique design style  to reduce the overlying vertical stress on the lowering area. and the temple at  Gangaikondacholapuram built by Rajendra Chola, son of Sri Rajaraja differs from this style.

Each wall of the sanctum holds intricate sculptures of various Shiva forms—Lingodbhava, Bhikshatana, Ardhanarishvara, and more—highlighting his all-encompassing nature. The inner walls also feature 81 carved Bharatanatyam dance poses from the Natya Sastra, indicating the early development of this classical dance.

The temple lacks a massive entrance gopuram and instead has fortified outer walls with cannon placements and a moat They  were built in the later period in late 1700s by the French forces . The European army occupied the temple for a short period and use the temple to store arms and ammunition. It was not built by the later Indian rulers.   

The uncovered pradakshina path circles the sanctum and adjoining mandapas, unlike typical covered corridors in other temples. This temple remains a model  of Chola engineering, art, and devotion to god.