The Dhananayagan Fort | Sathyamangalam, Tamil Nadu |

Bhavani Sagar Dam aka Bhavani Sagar Dam and Reservoir is the prominent earthen dam in India. The second largest dam in Tamil Nadu is located on the Bhavani River in Erode district, of Tamil Nadu. The dam with a capacity to store 32.8 tmc of water feeds the Lower Bhavani Project Canal and forms the water source for the vast swathes of land (2.45 lac acres) in Erode & Tiruppur Districts. The irrigation project was the first major irrigation project designed and developed in India after independence in 1947 and came to full function by 1956. It is one of the favorite places for picnics and is known for children's amusement, fun, and joy.

Whenever the water level in Bhavani Sagar Dam goes down (total height of the dam - 32 m (105 ft) the visitors can view the Danayakkan Kottai ‘டனாய்க்கன் கோட்டை’ aka Dhana Nayakan fort. Whenever the water level reaches full height the fort gets submerged into the water. According to historians the fort dates back to 1292 and 1341. Before the construction of Bhavanisagar Dam and Reservoir the present catchment area of the dam was occupied by the Dhana Nayakan fort as well as villages like Kooduvoy (கூடுவாய்), Peerkadavu (பீர்க்கடவு) and Kuyyanur (குய்யனூர்). Once it was decided to construct the dam the native people were provided with alternate land for living. The fort also bears some significant inscriptions.

This region was known as part of Kongu Nadu. Valasundara Kavirayar, probably a seventeenth century poet, hailing from Vijayamangalam (near Perundurai) versifies the borders of the Kongu mandalam as:

வடக்கு நந்திகிரி வராககிரி தெற்குகுடக்கு பொறுப்பு வெள்ளிக்குன்றுகளித்தன்டலை மேவு காவிரிசூழ்நாடு-குளித்தன்டலை அளவு கொங்கு. - கொங்குமண்டல சதகம்
According to his poem in Kongumandala sathakam (கொங்குமண்டல சதகம்), the Kongu Nadu was bound by Varaka Giri (Panrimalai mountain (பன்றிமலை) in the Palani-Kodaikkanal ranges (பழனி கொடைக்கானல் மலை) in the south, Kudagu (குடகு) and Vellikundru (வெள்ளிக்குன்று) (Kodagu (கொடகு) in the Madikeri dist. of Karnataka and Vellingiri hills (வெள்ளிங்கிரி) near Coimbatore) in the east and Nandigiri (நந்திகிரி) (Nandi hills in Kolar and Tumkur dists. of Karnataka) in the north. The native communities of Kongu Nadu includes Kongar (கொங்கர்), Kosar (கோசர்), Aviyar (அவியர்), Oviyar (ஓவியர்), Veliyar (வெளியர்), Velir (வேளிர்) etc. Agriculture was the major occupation of many of the people in and around this vast region.

The ancient Kongu country was ruled over by the Velir chiefs. Sources indicate about an active trade between Kongu and the classical Romans during this period. At the end of Sangam Period from about 300 A.D.- 600 A.D., there is a lack of coherent information on the history of Kongu Nadu. The South Western region of Kongu was occupied by Chera rulers; South Eastern part by Pandya kings. Adiyas and Kadavas possessed Northern Kongu.

Imperial Cholas ruled the Kongu region except the south and south-western region which were controlled by the Pandyas and the Chera kings of the Perumal dynasty. During the 10th century A.D., Kongu came under autonomous rule of the members of the collateral Chera family for nearly 300 years and they assumed the titles and names of Imperial Cholas. Thereafter the Pandyas ruled for some time.

Hoysalas, a prominent Southern Indian Kannadiga empire, ruled most of the modern-day state of Karnataka and parts of Tamil Nadu. The loss of Vira Someshwara (1235–1263) against Jatavarman Sundara Pandiyan resulted in the end of the Hoysala Empire. Jatavarman Sundara Pandiyan went inside Kannada country after conquering Tiruchy and occupied parts of Hoysala territory up to the Konkana coast and established his son Vira Pandiyan as ruler of those territories. The Imperial Cholas made alliance with Hoysalas and this alliance with the Hoysalas did no good to the Cholas and with the death of Vira Someshwara. The Pandyans got hold of the Kongu territories, Chola Nadu and some of the Hoysala countries during the time and a new clan called Kongu Pandiyar (கொங்கு பாண்டியர்கள்) was established under Jatavarman Vira Pandiyan.

Courtesy @muthusamyphotostream.blogspot.com/2015/09/dandanayakan-fort-hoysala-commanders.html