On Tuesdays and Saturdays, un-castrated male animals, primarily goats and roosters, are brought to the temple to be sacrificed to Kali. Not for the faint of heart, a visit on these days allows you to witness the steady stream of worshippers bringing their animals to the river where they're quickly killed and butchered. The animal remains are either taken home or cooked up outside the temple in a great feast.
Non-Hindus are not permitted inside the temple itself, but you can take pictures of the exterior and shop at the stalls lining the path that leads to the temple. While the sacrifices may be startling and fascinating, they are sacred to those performing them, so it's important to be respectful and discreet when observing or taking photographs.