The creatures that adorn it are remarkably lifelike because they were cast from actual organisms by a method something like the lost wax process. The body was carefully enclosed in plaster, which was then heated in a kiln until all the organic matter burned away. Then silver was poured in.
This method was very common in the 16th century. Most of the models were ordinary animals the artists found in their own gardens.
Extraordinary. You can read more about the method here.