@Zaz: I think the zoo management wanted a "hotel" look for the entrance; the firm that designed it is renowned for their work on modern-tropical hotels and houses.
Though seemingly extravagant, there are also practical reasons to the design of the entrance plaza. The high ceilings provide natural ventilation and allows sunlight in. And the extensive built-up area is necessary as it rains a lot here; the entrance needs to be expansive enough to hold large crowds caught by sudden downpours.
