Ground-penetrating radar (GPR) enables inspection of optically opaque media and provides information about buried or otherwise hidden targets. This makes GPR an especially useful tool for monitoring and investigating cultural-heritage (CH) and archeological sites. This article reviews theoretical and practical aspects of GPR for its effective and reliable use in CH applications. Data processing via a linearized microwave tomographic (MWT) approach is our main focus. Theoretical and practical issues related to GPR imaging, such as the mitigation of clutter and artifacts as well as 3D reconstruction of large spatial domains, are addressed in this context. Finally, we explain how GPR was applied in a survey performed at the archeological site of Pompeii, Italy.