Source: http://www.atlasobscura.com/places/lujan...

Anyone wanting to talk with the animals, walk with the animals, or even climb on the animals will be well served at Argentina's Lujan Zoo, where even the most dangerous predators are supposedly taught to cuddle up to humans by raising them alongside dogs. 

According to zoo officials, this docile attitude is achieved via two methods. The most obvious is by keeping the creatures constantly full and well-fed so that they don't ever think of humans as food. The other method involves raising the massive predators alongside canines. Supposedly the wild animals learn to mimic the domesticated dogs' affection for humans, leaving them irreversibly heart-warming. However not everyone is convinced that these methods work, or even exist.

Despite largely positive reviews across a number of travel sites, the zoo has also garnered negative descriptions with some visitors noting that the animals seemed incredibly lethargic, as though they had been chemically sedated. Animal rights groups have also claimed that no amount of training or feeding could produce the level of passivity on display at the Lujan Zoo. The zoo claims that the level of sedation they are accused of is impossible as it would simply kill the animals. No matter how sleepy the tigers seem, no concrete evidence on either side of the argument has come to light.