In reality, the 1,620-hectare (4,000-acre) Barro Colorado Island is a hilltop. Or, at least it was until the creation of Gatún Lake turned it into the largest island in the Canal Zone, one where the Smithsonian Institute operates a research center and gives morning tours. Ships sail tightly past the island, offering the chance to glimpse toucans, iguanas and bats that live among the 1,300 plant species and 381 bird species of this vital tropical woodland.