The Calusa were expert builders as well as excellent fishermen. Historians believe the tribe used sea shells together with bones and charcoal remains as raw materials for building artificial islands. Of these islands, Mound Key, the capital of the Calusa, was the largest. It is also the one that anthropologist Victor Thompson, a professor at the University of Georgia, and his team of researchers explored to better understand its composition and the changes it underwent over time. 

Complex analysis procedures, such as core drilling and radiocarbon dating, revealed that the composition of Mound Key is not homogeneous.

According to researchers, the presence of more recent material in the depths of the island instead of on the top, as would be logical to assume, could be explained by the temporary abandonment of the island due to climate changes that would have made fishing difficult. Only at a later stage, Mound Key was repopulated and remodeled with new material.

But that’s not all. According to Thompson, the king’s palace built by the Calusa on the island, was an imposing oval-shaped structure, more than 24 meters long and more than 20 meters wide, that occupied almost the entire area of Mound Key and capable of accommodating up to 2,000 people. Researchers have documented that the palace was built in at least three phases, using raw materials, some of which were imported from overseas, such as lumber. The grandeur of the palace only confirms the hypothesis that the Calusa society was very well developed and organized, with a large workforce that contributed greatly to the construction of the palace.