A puteal is an old-fashioned structure built around the hole of a well. It is made to stop people from easily falling in. Some puteals have bas relief. Some have a step that leads to the water well itself.
Puteals were decoration or part of an architectural design.
In the big places where a lot of people walked in Venice, puteals had cast-iron lids. That protected people even more and stopped the water supply from becoming dirty.
Classically, puteals were made of carved stone, or marble in Europe. They were in big private courtyards and town/city squares.