Inspired by the Basilica group B, we describe a general construction which allows us to associate to any group of automorphisms G Ä Aut.T / of a rooted tree T a family of Basilica groups Bas s .G/, s 2 N C . For the dyadic odometer O 2 , one has B D Bas 2 .O 2 /. We study which properties of groups acting on rooted trees are preserved under this operation. Introducing some techniques for handling Bas s .G/, in case G fulfills some branching conditions, we are able to calculate the Hausdorff dimension of the Basilica groups associated to certain GGS-groups and of generalisations of the odometer, O d m . Furthermore, we study the structure of groups of type Bas s .O d m / and prove an analogue of the congruence subgroup property in the case m D p, a prime.