Start with the reason you came here - the Annai Velankanni Church which is dedicated to Our Lady of Good Health. This basilica is famous for its miraculous healing. The church’s well-designed architecture depicts the Gothic style which is unique in India. You can attend one of the two masses conducted that day if time permits - one in the morning and one in the evening.
Start the day with a visit to Guindy National Park, that boasts a rich variety of flora and fauna making it one of the most visited national parks in India. The park features a children's park, a library, a snake park, and a Butterfly Park. You can also take a safari ride and explore the wildlife in the park.
If you have extra time, you can visit the Government Museum which is a 30-minute drive away from the church. It houses the finest collection of Roman antiques outside Europe. You can also take a rickshaw ride and explore the city's bazaars and markets selling souvenirs and traditional Indian clothing. If you are interested in history, plan your visit to coincide with the Madras Week festival in August which commemorates the city's founding.