How to build a REALLY big a retaining wall, 11 ft high x 100ft wide retaining wall being built out of concrete and steel is discussed at Austin custom home builder’s site, Jenkins Custom Homes,
Concrete Foundations and Retaining Walls
Originally, foundations would be placed in to the ground, connected to one another, and then built on top of. These foundations were typically constructed using wood, but concrete was introduced to provide a stronger and longer-lived functionality. These days, the most effective are known as precast concrete foundations and footings. These lay underground, provide a solid foundation for construction, and can last for decades without even the slightest need for repair.