Kaveri which is also known as "Dakshin Ganga" is the major river of Tamilnadu. The origin of this river is the hills of Coorg, Karnataka and ends in the Bay of Bengal.

Most of the soils of the plains of Tamil Nadu are alluvial, formed by rivers flowing east.

Geographically, Tamil Nadu may be divided into four physical divisions.

 The Nilgiri Hills are part of a larger mountain chain known as the Western Ghats. Their highest point is the mountain of Doddabetta, height 2,637 m. The district is contained mainly within the Nilgiri Mountains range. The administrative headquarters is located at Ooty (Ootacamund or Udhagamandalam).

Annapurna peak--Annapurna is a massif in the Himalayas in north-central Nepal that includes one peak over 8,000 metres (26,000 ft).

Gurushikar peak-- Guru Shikhar, a peak in the Arbuda Mountains of Rajasthan, is the highest point of the Aravalli Range. It rises to an elevation of 1,722 metres .

Gangotri peak-- It is in  Uttarakhand. Gangotri I (6672m) is the tallest peak of the Gangotri massif which has 3 peaks above 6000m, it is part of the Gangotri group of mountains in Garhwal Himalaya.

The valley between Thekkadi hills, Varshanadu hills and Kodaikanal hills is known as Kambam valley. This valley is considered as the green valley of Tamil Nadu.

The Western hilly region is much more complex than the Eastern Ghats.

Though the Western Ghats is a continuous range, it has a gap of 25 km at Palghat. To the south of Palghat gap, hills such as Andipatti, Elamalai and Agathiya malai are found.

The average height of the Western hilly region is from 1000 m to 1500 m.

From the Nilgiris of Tamil Nadu and Anaimalai hills of Kerala, an offshoot runs at a height of 1500 m to 2000 m in the east. These are called Palani hills.

To the south of Palani hills, there are two other ranges namely, Varshanadu and Andipatti hills running parallel to the Cardamom hills.

• The gap in between Varshanadu hills and Agathiya malai is called the Shenkottai pass.

The Palakkad gap and Shenkottai gap are the only breaks in the long chain of hills that border Tamil Nadu on the west.

• Doddabetta is the highest mountain in the Nilgiri hills at 2,637 metres (8,650 feet).

• Plateaus of Tamil Nadu can be grouped into two as Coimbatore plateau and Madurai plateau. 

The Western Ghats and Eastern Ghats meet at the Nilgiri Hills.

• At least 24 of the Nilgiri mountains' peaks are above 2,000 metres (6,600 ft), the highest peak being Doddabetta, at 2,637 metres (8,652 ft).

There are two types of plains in Tamil Nadu which are coastal plains and river plains. The coastal plains of Tamil Nadu extent from Publicat lake in the north to Kanyakumari  in the South, to a length of 1,000km at an average elevation of 50mt. The notable beaches found here are the Marina beach and the Rameshwaram beach.

The Coastline of Tamil Nadu is located on the southeast coast of Indian Peninsula, and forms a part of Coromandel Coast of Bay of Bengal and Indian Ocean. It is 1,000 km long and is the second-longest coastline in the country after Gujarat. 

The Eastern Ghats are not continuous when compared to the Western Ghats. They are dissected into isolated hill ranges extending from northeast to southwest through the districts of Vellore, Dharmapuri and Erode.

The Eastern and Western Ghats meet at the Nilgiris plateau. Four km from this plateau, it slopes gently downwards to about 1,800 m towards Coimbatore.

The Western Ghats has mountain peaks namely Doddabetta (2637 m) and Mukuruthi (2540 m).

The Bramahal plateau in Dharmapuri district is at an elevation of 300 to 700 m which merges with the Mysore plateau in the west.

The Nilgiris plateau extends from the Nilgiris to Dharmapuri plateau or Bramahal plateau and lies to the west of Shervaroy uplands. This plateau is found with extreme abruptness on all sides.

The main river of Tamil Nadu is Kaveri which originates in Kodagu district of Karnataka. Kaveri and its tributaries in its lower coursen drain the districts of Nagapattinam, Thanjavur, Thiruvarur and Tiruchirapalli. The Kaveri, the Kollidam and the Vellar jointly drain central part of the Tamil Nadu.

River Kollidam branches off from Kaveri at Grand Anaicut (Kallanai).

The Tamil Nadu plain stretches for 675 km from Pulicat lake to Kanyakumari along the coast of Tamil Nadu. Its average width is 100 km. The most important feature of this plain is the Cauvery delta where the plain is 130 km wide. The fertile soil and large scale irrigation facilities have made the Cauvery delta the granary of South India.

The river plains in Tamil Nadu are formed by the river Palar, Cheyyar, Pennar and Vellar in the north; Kaveri and its tributaries in the central region; Vaigai, Vaippar and Thamirabarani in the south.

The head of the Kaveri delta is near the island of Srirangam.

• The second largest beach in the world, Marina Beach, extends up to 13 km.
  
• Marina Beach is one of the major tourist attractions in Chennai. 

Kaveri, along with its tributaries Bhavani, Noyyal, Moyar and Amaravathi, is the most important source of canal irrigation. The river's basin covers four states and Union Territories, as follows: Tamil Nadu, Karnataka, Kerala, and Puducherry. The Kavri delta, the distributaries such as Kollidam, Maniyar, Vennar, Vettar, Arasalar, Nettar etc. form an alluvial plain in the quadrangle shape. Towards the south of Tamil Nadu, there are few rivers like Vaigai, Vaippar, Thamirabarani and Kothayar etc.

The river plains in Tamil Nadu are formed by the river Palar, Cheyyar, Pennar and Vellar in the north; Kaveri and its tributaries in the central region; Vaigai, Vaippar and Thamirabarani in the south.

The river plains in Tamil Nadu are formed by the river Palar, Cheyyar, Pennar and Vellar in the north; Kaveri and its tributaries in the central region; Vaigai, Vaippar and Thamirabarani in the south.

The coastal plains of Thiruvallur, Kancheepuram, Cuddalore and Villupuram are together known as the Cholamandalam plains. Ramanathapuram is not the part of Cholamandalam plains.