Open caissons are large, hollow structures used in construction to create deep foundations. They are typically made of reinforced concrete and are designed to be sunk into the ground, allowing workers to excavate soil from inside. This method is particularly useful in areas with water or soft soil, as it provides stability during the construction process. Once the caisson reaches the desired depth, it is filled with concrete to create a solid base for structures like bridges or buildings. Open caissons are often used in conjunction with other foundation techniques, such as piles or drilled shafts, to ensure a strong and durable foundation.