The paper outlines the domains of enterprise architecture and basic requirements of “architectures in the large”. A methodology for the description of enterprise architectures is introduced. It is based on three basic views on architecture. The component view describes the elements of architecture and their relationships. The communication view shows how the elements interact with one another. The distribution view describes how the elements are distributed in terms of location or organizational assignment. Based on the three basic views on architecture, complexity can be reduced and elementary construction principles of the architecture can be highlighted. Key element of architecture design is to account for interdependencies among the building blocks of architecture. Blueprints are introduced as a means in planning the deployment of architecture on a large scale. Blueprints give a comprehensive view on the building blocks and how the interact. They show the effects of architecture design between business, application, and infrastructure architecture. The techniques introduced for architecture design are illustrated by using a selection of real life examples from an architecture design project at Siemens AG.