Model-driven software engineering intends to reduce development effort by generating executable code from high-level models. However, models for non-trivial problems are still very large and require sophisticated support for modeling-in-the-large--a challenge which has not yet gained sufficient attention in model-driven software engineering. In response to this need, we have developed a set of tools for modeling-in-the-large based on UML package diagrams. The tool set comprises a stand-alone tool, which serves as a graphical editor for package diagrams, an integration tool, which controls the consistency of the model with its architecture defined in the package diagram, and a metrics tool, which is used to measure the coupling of model packages. Our tools for modeling-in-the-large complement the functionality of an environment for model-driven software engineering which so far has focused on supporting modeling-in-the-small. The overall environment has been applied successfully in a project which is dedicated to model-driven engineering of a product line for software configuration management systems.