Janpath Rd, Rajpath Area, Central Secretariat, New Delhi, Delhi 110011, India
The National Museum is fully air-conditioned. It's among the largest museums in India, and you could spend the whole day browsing through its galleries. The collection consists of about 200,000 objects, mainly from the Indus Valley Civilization (also known as the Harappan period) dating as far back as 2,500 BC. Other items include bronze statues from the Chola Dynasty, Buddhist relics, coins, textiles, musical instruments, tribal artifacts, armor, decorative arts, and miniature paintings.
If you're interested in history, the Indira Gandhi Memorial Museum is dedicated to controversial former Prime Minister Indira Gandhi, who was assassinated in 1984. She was India's first female prime minister, and her residence (where she was killed) has been turned into the museum. The National Rail Museum showcases India's rail heritage and is popular with families. Many exhibits are outside, but its indoor gallery is air-conditioned. The National Science Center is an interesting museum devoted to science, and is another air-conditioned option.