Srirangapatna is a historical town in Mandya district of Karnataka. Located near the city of Mysore, Srirangapatna is among the popular tourist places in Karnataka owing to its cultural, religious and historic importance and also one of the top places to visit in Mysore. The entire town is surrounded by the river Kaveri to form a river island.

The town takes its name from the celebrated Ranganathaswamy temple which dominates the town, making Srirangapatna one of the most important Vaishnavite centers of pilgrimage in South India. The temple was built by the Ganga dynasty rulers of the area in the 9th century; the structure was strengthened and improved upon architecturally some three centuries later. Thus, the temple is a medley of the Hoysala and Vijayanagar styles of temple architecture.

Tradition holds that all the islands formed in the Kaveri River are consecrated to Sri Ranganathaswamy, and large temples have been built in very ancient times dedicated to that deity on the three largest islands. These three towns, which constitute the main pilgrimage centers dedicated to Ranganathaswamy, are: Adi Ranga – at Srirangapatna: Madhya Ranga – at Shivanasamudra; Antya Ranga – at Srirangam

The presence of the Kaveri River is in itself considered auspicious and sanctifying. The Paschima Vaahini section of the Kaveri at Srirangapatna is considered especially sacred; the pious come from far and wide to immerse the ashes of the departed and perform obsequies to their ancestors in these waters.

The Ranganathaswamy temple:  It is one of the five important pilgrimage sites of Sri Vaishnavism along the river Kaveri for devotees of Ranganatha. These five sacred sites are together known as Pancharanga Kshetrams in Southern India. Since Srirangapatna is the first temple starting from upstream, the deity is known as Adi Ranga (lit; “first Ranga”).  The other being:

The main deity here is Lord Ranganatha who is a manifestation of Lord Vishnu. Idol of the Lord is in resting posture on a bed of serpent Aadi Sesha. Aadi Sesha is said to have seven heads and is often depicted with the Lord Vishnu. The main entrance has Chaturvimsati (four) pillars has the cravings of the 24 forms of Vishnu. It is said that this is one of the biggest idols of Lord Vishnu in the reclining posture. Idol of Goddess Lakshmi b the side of Lord’s feet can also be seen. Goddess Ranganayaki is considered to be the principal goddess here. Other shrines inside the temple complex are Srinivasa, Ranganayaki, Rama, Narasimha, Sudarshana, Panchamukha Anjaneya and Gopalakrishna.

The best time to visit Sri Ranganatha Swamy Temple is during Kotarothsava festival. This festival which is dedicated to Lord Ranganatha, is celebrated with great vigour and grandeur.

Nimishamba Temple: The famous Nimishamba (the incarnation of Parvathi, the goddess wife of Lord Shiva) temple is on the bank of the Lokapavani river. This temple can be clearly seen from the top of the Karighatta hill. It is a belief that Goddess Parvathi clears all the problems and troubles of her devotees within a minute (nimisha in Sanskrit), and hence the name.

Source:

https://www.karnataka.com/srirangapatna/sri-ranganathaswamy-temple/

https://en.wikipedia.org/wiki/Ranganathaswamy_Temple,_Srirangapatna

http://www.mysoretourism.org.in/sri-ranganathaswamy-temple-mysore

http://sriranganathaswamytemple.kar.nic.in/