The paper introduces a novel multivariable laboratory process called the quadruple-tank process, which consists of four interconnected water tanks and two pumps. The system's linearized dynamics include a multivariable zero that can be moved along the real axis by adjusting the valve settings, allowing it to be placed in either the left or right half-plane. This feature makes the quadruple-tank process ideal for illustrating various concepts in multivariable control, particularly performance limitations due to multivariable right half-plane zeros. The location and direction of the zero have physical interpretations, making the process suitable for educational purposes. The paper derives accurate models from both physical and experimental data and demonstrates decentralized control on the process. The quadruple-tank process is simple to build and can be used to illustrate multivariable zero location and direction, as well as the impact of right half-plane zeros on control performance. The paper also discusses the nonlinear model of the process, the relative gain array, and the identification of the system using experimental data. Decentralized PI control is applied to the process, showing that the nonminimum-phase setting is more difficult to control than the minimum-phase setting. The quadruple-tank process is currently used in control education at several institutions.The paper introduces a novel multivariable laboratory process called the quadruple-tank process, which consists of four interconnected water tanks and two pumps. The system's linearized dynamics include a multivariable zero that can be moved along the real axis by adjusting the valve settings, allowing it to be placed in either the left or right half-plane. This feature makes the quadruple-tank process ideal for illustrating various concepts in multivariable control, particularly performance limitations due to multivariable right half-plane zeros. The location and direction of the zero have physical interpretations, making the process suitable for educational purposes. The paper derives accurate models from both physical and experimental data and demonstrates decentralized control on the process. The quadruple-tank process is simple to build and can be used to illustrate multivariable zero location and direction, as well as the impact of right half-plane zeros on control performance. The paper also discusses the nonlinear model of the process, the relative gain array, and the identification of the system using experimental data. Decentralized PI control is applied to the process, showing that the nonminimum-phase setting is more difficult to control than the minimum-phase setting. The quadruple-tank process is currently used in control education at several institutions.