More than 400 million Hindu pilgrims gathered in a temporary megacity for the world’s largest religious gathering—and photographer and National Geographic Explorer George Steinmetz was in India to document the joyful weeks-long celebration. Held at the sacred confluence of the Ganges, Yamuna, and mythical Saraswati Rivers, the Mahakumbh Mela only happens once every 144 years. This photo of the once-in-a-lifetime event is among National Geographic’s Pictures of the Year.

The world’s tiger population was under dire threat by the 1990s. But a group of valiant individuals worked together to change the fate of Earth’s largest cats. Tigers like Sita—pictured above taking care of her cub—became living proof that this endangered species can flourish if only given enough room and enough prey. Scroll through this beautifully photographed feature to see the harrowing fight to save the tigers.

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