The recent advance of seismic metamaterials has led to various concepts for the attenuation of seismic waves, one of them being the locally resonant metamaterial. Based on this concept, the so-called metafoundation has been designed. It can effectively protect a fuel storage tank from ground motions at various fluid levels. In order to show the effectiveness of the proposed design, the response of the metafoundation is compared to the response of a tank on a traditional concrete foundation. The design process of conceiving the metafoundation, optimizing it for a specific tank, and its seismic response are described herein. Furthermore, the response of a tank during a seismic event can cause severe damages to pipelines connected to the tank. This phenomenon can be of critical importance for the design of a seismic tank protection system and must be treated with care. Since the coupled structure (tank + foundation + pipeline) exerts highly nonlinear behavior, due to the complexity of the piping system, a laboratory experiment has been conducted. More precisely, a hybrid simulation (HS) that uses the metafoundation and a tank as a numerical substructure (NS) and a piping system as a physical substructure (PS) was employed. To make the results relatable to the current state of the art, additional experiments were performed with concave sliding bearings (CSBs) as an isolation system in the NS. The metafoundation offered a clear attenuation of tank stresses and, in some cases, also reduced the stresses in the piping system.