Aquariums have long offered a window into the underwater worlds that most will never have the chance to explore in the wild. While a typical home aquarium might contain 29 to 30 gallons of water, the globe’s most impressive public aquariums eclipse this figure many times over. These are places where the giants of the ocean—the whale sharks and the manta rays—are not just residents but the main attractions. These are the largest aquariums in the world.