Old fashioned thermal container
The cork oak (Quercus suber), native to southern Europe and most common tree found in Alentejo (the southern part of Portugal just north of the Algarve), is used since ancient times not only to produce corks for the local wine but to create several other objects.
This is a "tarro", it is basically a traditional food recipient that would allow taking hot food to workers in the cereal fields.
The craftsmanship is extremely simple: cut a section of the tree trunk, hollow it from the wood except in the bottom and voilá thermal insulation used even before the Romans invaded the Peninsula some say.