Open caissons are large, hollow structures used in construction, particularly for building foundations in water or soft soil. They are typically made of reinforced concrete and are designed to be sunk into the ground or underwater. The open top allows for excavation and the removal of soil, enabling the caisson to settle into place. Once the caisson reaches the desired depth, it is filled with concrete to create a solid foundation. This method is often used in projects like bridges and piers, where stability is crucial. Open caissons are effective in areas where traditional deep foundations may not be feasible due to environmental conditions.