Several islands in the Islamorada area have become state parks to preserve and protect the natural environments. Indian Key, Lignum Vitae Key, Shell Key and Cotton Key are all accessible only by boat. Two of these islands are suitable for exploring: Indian Key and Lignum Vitae Key. Each is very different. So a visit to each one sometime during your Keys vacation is strongly recommended. Indian Key is a State Archeological Site with ruins that date back to the mid 1800's. Lignum Vitae Key is a State Botanical Site with many endangered tropical hardwood trees and the coral rock house pictured above.. Shell Key and Cotton Key are not really suitable for exploration as they are low and swampy and are best left to the wildlife.