Cassia Testa Gallas
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It's a great place to enjoy nature and see the native blue iguanas.
Due to the amount of plants the temperature is a bit cooler than other areas of the island (but still very hot during summer, so either go early morning or around 4pm).
There are lovely play areas for kids, and a typical caymanian house for visitors to learn about life in Cayman in the old times.
Incredible biodiversity of plans, insects and so forth.
The gift shop accepts cards and has some good options of souvenirs, including plush blue iguanas.
Make sure to apply sunscreen and bug spray before going, bring water and wear a hat.