As the air-conditioned bus weaves through the bustling traffic of the eastern Indian city of Kolkata, tour leader Sujoy Sen lists the many sights on the itinerary.

It sounds like a snapshot of the city's cosmopolitan history—colonial buildings like the General Post Office and the former British viceroy's mansion, Hindu and Jain temples, Greek Orthodox and Portuguese churches, an Anglican cathedral, homes of freedom fighters who fought the British Raj, and prosperous Indian merchants. But unlike most heritage tours, this one happens after sundown. And its main focus is not just the history or architecture but the lights illuminating the buildings.

The Kolkata Illumination Project is the latest addition to the city's many heritage tours and walks. Mr. Sen, who runs a tour company, came upon a newspaper article about city enthusiasts lighting up some of the city's neglected heritage buildings. He checked them out and was stunned. 'I have seen Paris by night. I didn't realize Kolkata could be like that also,' he says.

The project is the brainchild of a citizens' group called Kolkata Restorers, which, according to Mudar Patherya, one of its driving forces, isn't a formal organization but merely a 'label' tied to a WhatsApp group.

Initially wanting to paint a neglected dome of an old market, Mr. Patherya realized the need to illuminate it so it could be seen at night. He extended the effort to light up more buildings, such as the Geological Survey of India and Raj Bhavan, the governor's mansion.

As of now, 92 buildings have been illuminated, achieved with minimal investment compared to the luxury real estate markets in the city. The goal is to reach 200 buildings and showcase Kolkata as one of the most beautiful cities at night in India.

The restoration efforts have also unveiled a deeper need—repairing the often crumbling structures before they can be beautifully lit. These community-driven efforts are not only reviving the illuminated architecture but are reigniting a shared pride and connection to Kolkata's heritage amongst its residents.