Rath temples of Mahabalipuram were built in the reign of Narasimhavarman I. There are about nine monolithic temples at Mahabalipuram. They are the unique contribution of the Pallavas to Indian art. The monolithic temples are called locally as Ratha (chariot) as they resemble the processional chariots of a temple. The five Rathas, the best of all monolithic temples, are hewn out of a huge boulder.

Introduction:
The Rath Temples at Mahabalipuram are a group of monolithic rock-cut temples located in Mahabalipuram, a UNESCO World Heritage site in Tamil Nadu, India. These temples were built during the reign of the Pallava dynasty, one of the most influential and creative dynasties in South Indian history. The temples are known for their exquisite architecture and intricate carvings, which reflect the artistic and architectural brilliance of the Pallava rulers.

Explanation:
The correct answer to the question is option 'B' - Narasinghvarman I. The Rath Temples at Mahabalipuram were built during the reign of Narasinghvarman I, also known as Mamalla Narasimhavarman I. He was a prominent ruler of the Pallava dynasty who reigned from 630 CE to 668 CE.

Narasinghvarman I was known for his military conquests and patronage of the arts and architecture. He was a skilled warrior and extended the boundaries of the Pallava kingdom through successful military campaigns. He is also credited with the construction of many magnificent temples and architectural marvels.

Significance of Rath Temples:
The Rath Temples at Mahabalipuram are a unique architectural marvel, representing the pinnacle of Pallava architectural style. These temples are carved out of large monolithic rocks and resemble chariots or raths, hence the name "Rath Temples."

The main Rath Temples at Mahabalipuram include the Dharmaraja Ratha, Arjuna Ratha, Bhima Ratha, and Draupadi Ratha. These temples are dedicated to various Hindu deities and are adorned with intricate carvings depicting mythological scenes, gods, goddesses, and celestial beings.

The Rath Temples showcase the Pallava style of architecture, characterized by their distinctive style of carving and intricate detailing. The sculptures on the walls of these temples depict various episodes from Hindu mythology, including the Mahabharata and Ramayana.

Conclusion:
The Rath Temples at Mahabalipuram are a testament to the architectural brilliance of the Pallava rulers, particularly Narasinghvarman I. These temples not only serve as a religious site but also stand as a testimony to the rich cultural heritage of Tamil Nadu. The intricate carvings and unique architectural style of the Rath Temples continue to attract tourists and art enthusiasts from around the world.