The Otter House Project tried to think like an otter when designing this habitat. Otters are intelligent, social animals and ZOO Architects tried to build these structures to meet their behaviors. Via DesignBoom:

The Otter House Project by ZOO Architects (see more here) focuses on how these animals usually live together and form family groups. Otters often sleep holding hands, which is a manifestation of their social behavior, and live together in families or groups, typically consisting of a pair of adult otters and their offspring. They communicate with each other through sounds, postures, and odors. The behavior of sleeping hand-in-hand usually occurs among family or group members, helping to strengthen their bonds and trust. Otters also practice monogamy, which means they manifest loyalty to their life partners.They will store enough food inside their nests to prepare for unexpected needs.

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