Kolkata boasts of one of the most-visited and largest museums in the country, the Indian Museum. It’s also the ninth oldest in the world (it was founded back in 1814). The most popular attractions are definitely the Egyptian ‘mummy’ (read more about it here) and relics from the Indus Valley civilisation. You could spend the better part of a morning here – there’s a lot to see.
Even though not all the rooms of the museum are air-conditioned, the rooms are pretty cool because of the high ceilings allowing for good ventilation. You might want to avoid going over the weekends (they tend to be far more crowded). You can now also tour the museum from the comfort of your own home. Read more about doing that here.