The Pallavas were the pioneer of the Dravida style of temple architecture. During the rule of Pallavas the cave architecture saw a new turn, monolithic temples and statues were built during their time. Three new styles of architecture : Anga, Mandapa and Rathas began to be built.
Must read: Pallava Dynasty : Foundation, Rulers, Capital, Administration, Architecture, Literature and Religion
The architecture of the Pallavas can be classified into four stages chronologically:
Mahendravarman Style of Architecture (610 AD-640 AD)
The temple architecture in South India and Pallava architecture began from the time of Mahendravarman I. This was the first stage of Pallava temple architecture. During his time a new style of building temples without making the use of bricks, iron, lime, wood, etc began to take place. The temples built under Mahendravarman I were basically rock-cut temples.
Fine examples of rock cut temples can be seen at Mahabalipuram. These rock cut temples were termed as ‘Mandapas’ unlike the Nagara style in which the mandapas meant only the assembly hall.
These Mandapas were the pillared Varamdas which consisted of Garbhagirha at the end. The Shaiva Garbhagrihas consisted of the statues of Lord Shiva and the Vaishnava Garbhagriha consisted of the statues of Lord Vaishnava.

Few famous Mandapas of Mahendravarman style of architecture are as follows:
Trimurti Mandapa of Mandaggapattu.
Panchapandava Mandapa of Pallvaram.
Mahendravishnu Mandapa of Mahendravadi.
Lalitankur Pallavaveshwar Griha Mandapa of Trichinapalli.
Mamalla Style or Narasimha Style of Architecture (640 AD-674 AD)
Mahabalipuram also known as Mamallapuram was the centre of architecture during the time of Narsimhavarman I. Mahabalipuram was established by Narsimhavarman.
This represented the second stage of the development of temple architecture in South India. The rock-cut temples were decorated with intricate sculptures. Under Narasimhavarman, the mandapas were now divided into separate rathas.
On sea shores of Mahabalipuram numerous monolithic rock cut cave temples and statues were constructed. In Mamalla style of architecture two styles of temples can be seen they are- a) Mandapas and b) Rathas.
The Mandapas of Mamalla style are more ornamental as compared to Mahendravarman style of Mandapas. The main features of these Mandapas are their pillars which are built on the heads of lions. Famous Mandapas of Mamalla style are- Varaha Mandapa, Mahisasur Mandapa and Pancha Pandava Mandapa, etc.

The second component of Mamalla style of architecture was the free-standing monolithic shrines called ‘Rathas’ (chariots) which were constructed alongside pillared halls. They were generally built of granite stones. The western architects calls these rathas as ‘Seven Pagodas’ or ‘Seven Rathas’ as they are seven in
number.
Draupadi ratha was the smallest ratha among all. It was designed like a hindu temple while other rathas were designed like Viharas or Chaityas. Dharmaraja ratha is one of the best example of ratha designed like Vihara. It is the biggest ratha among all the rathas of Mamalla style. The Bhim ratha and the Ganesha ratha are the best examples of the rathas built in the shape of Chaitya.
Rajasimha Style of Architecture (695 AD-730 AD)
This style of Architecture was begun by Narsimhavarman II Rajsimha. In this style of architecture the temples were now built by making the use of bricks, woods, stones,etc.. A few examples of the Rajasimha style of architecture are- Shore temple, Ishwariya temple, Mukunda temple, etc.
The Shore temple of Mahabalipuram is considered to be the best art of this style of architecture. It is also included in the UNESCO world heritage.

The Kailasha temple of Kanchipuram can also be considered as one of the finest art of Rajasimha style of architecture. The construction of this temple was began by Rajasimha but was completed by Mahendravarman II. It consists of almost all the elements of Dravida style such as Gopuram, Pillars, Mandapas, Vimana, etc.
Another famous temple of this style is Vaikunthaperumal temple which was built by Parmeshwarvarman II. It was dedicated to Bhagwat religion. The internal walls of this temple consists of the paintings of scenes of war, coronation, ashwamedha yajana, etc.
Nandivarman Style of Architecture/ Aparajitvarman Style (800AD-900AD)
After the decline of the Rajasimha style of architecture the Pallava architecture began to decline. The weak Pallava rulers were no more capable of building huge temples and monuments. The temples of this style were comparatively smaller in size less ornamented and also lacked innovation.

The famous temples of this style of architecture are- Mukteshawara temple and Matangeshwara temple of Kanchi.
Architecture and Sculpture at Mahabalipuram (Mamallapuram)
The ancient port city of Mamallapuram (Mahabalipuram) under Pallava dynasty in Tamil Nadu, flourished with a number of marvelous architecture. This 7th century Pallava site was declared as UNESCO World Heritage Site in 1984 by the name “Group of Monuments at Mahabalipuram”. They include:
Ratha Temples or Pancha Ratha:

Also known as Panchapandava Rathas, they are the earliest rock cut temples in India, comprising of Dharmaraja Ratha, Bhima Ratha, Arjuna Ratha, Nakula and Sahadeva Ratha, and Draupadi Ratha dated around 7th century AD.
The most exquisite of the five is the Dharmaraja Ratha, with a three-storied vimana and a square base. The Bhima Ratha is rectangular in plan and has beautiful sculptures of Harihara, Brahma, Vishnu, Skanda, Ardhanarisvara and Siva as Gangadhara. The Arjuna Ratha contains artistically carved sculptures of Siva, Vishnu, mithuna and dwarapala.
Rock-cut Caves:

They include Varaha Cave Temple, Krishna Cave Temple, Panchapandava Cave Temple, and the Mahishasuramardini Mandapa (Bas-relief of Goddess Durga killing Mahishasura).
Shore Temple Complex:

The iconic Shore Temple of Pallavas at Mamallapuram (Mahabalipuram) was constructed during the reign of Rajasimha (700-728). The temple comprises three shrines, where the prominent ones are dedicated to Siva and Vishnu.
The interior of the boundary wall of the shrine are elaborately carved and sculpted. In southern India, this is one amongst the earliest and most important structural temples. Unlike other structures of the region, the Shore Temple is a five-storeyed rock-cut monolith. The monolithic vimanas are peculiar to Mamallapuram.
Open Air Rock Reliefs:

It includes the Descent of the Ganga (variously described as ‘Bhagiratha’s Penance’ or ‘Arjuna’s Penance’). It narrates the story of descent of River Ganga on earth from heaven by the efforts of Bhagiratha. In close proximity lies a big rock boulder, known as Krishna’s Butter Ball.
The portrayal of puranic figures with popular local stories reveals the skill of the artists in blending various aspects of human and animal life. The sculptural panel in the Krishna mandapa, where village life with cows and cowherds is depicted with beauty and skill, is yet another artistic wonder to behold.