The largest and the oldest Shiva temple at Kumbakonam is dedicated to Lord Kumbeswara and Goddess Sri Mangalambigai. The temple is an architectural and sculptural gem with a 128-ft high Gopuram carved intricately. It houses a shrine of Adi Vinayaka (Lord Ganesha) and Navarathri Mandapam that enshrines a single block of stone on which all the 27 stars and 12 Rashis (zodiacs) have been carved out. The temple also enshrines a rare specimen of the image of Lord Subrahmanya with six heads and six hands with different kinds of weapons. The temple also has an extensive collection of silver 'vahanas' (chariots) that are used carry the deities around at festival times. It was originally built by a Chola ruler only to be renovated later by the Nayak King. However, some of the old antique idols are still enshrined here such as those of 'Sri Ambal', 'Sri Durgaiamman' and 'Sri Kirathamoorti'.

According the legend that after the Great Floods, Lord Shiva set a 'Kumbam' (Pot) full of amirtham and seeds for creation afloat and proclaimed that the place where the pot touched the ground would be considered as the holiest places in the world. It came to rest at Kumbam, later deformed to 'Kumbakonam'. Lord Shiva appeared as a hunter and broke the pot with his arrow. While the divine nectar from the pot became the famous Mahamaham Tank, Shiva made a ShivaLinga out of the broken pot pieces and entered it. Thus he came to be known as Adi Kumbeswara and is said to be enshrined here in this temple. Unlike other temples, the MahaLinga here is not made up of granite stone. The great Mahamaham festival is celebrated in honor of the Lord once in every 12 years and attracts thousands of pilgrims.