Start your day with a visit to Guindy National Park, one of the smallest national parks in India. The park is home to a variety of flora and fauna, including blackbucks, spotted deers, and various species of birds. Take a morning walk on the designated trails and enjoy the lush green surroundings. Afternoon, you can visit the Children's Park and Snake Park located inside the National Park, which is a big hit with kids. In the evening, you can spend time in the beautiful Rose Garden, which has over 170 varieties of roses.
On your second day, head towards Pulicat Lake, which is the second-largest saltwater lake in India. It is a perfect spot for bird watching, and you can spot various migratory birds like flamingos, pelicans, and kingfishers. In the morning, you can take a boat ride and explore the lake's beauty, and later you can visit the Dutch Fort, built-in 1609, which is now in ruins but still worth a visit. In the afternoon, you can visit the nearby Sriharikota Island, which is India's main spaceport and visit the Satish Dhawan Space Centre. In the evening, you can watch the sunset at the beach and enjoy the local seafood.
If you're interested in history, you can visit Fort St. George, which was built-in 1644 by the British East India Company. You can also visit the Government Museum, which has a vast collection of archaeological and cultural artefacts. If you're interested in temples, visit the Kapaleeshwarar Temple, which is dedicated to Lord Shiva and built-in the 7th century. If you have an extra day, you can visit the Mahabalipuram, which is 57 km from Chennai and has UNESCO World Heritage sites like the Shore Temple and Five Rathas.