An engineered approach to the design of mobile agent applications requires appropriate abstractions for both the space where agents move and the conceptual space of mobile agent interaction. The paper introduces the HiMAT framework for mobile agent applications, which models the Internet as a collection of hierarchical domains, where programmable coordination media rule mobile agent's interaction within each domain and locally to each node. This provides the designers of mobile agent systems with a single, coherent framework enabling them to effectively deal with network topology, authentication, authorisation and coordination in a uniform way.