Domain-specific languages (DSL) receive a constantly growing attention in the area of software development. However, so far the documentation of reusable architectural knowledge for DSL design is rather limited. In this paper, we systematically explore the DSL design space by combining reusable architectural decision modeling and software patterns. In particular, we have explored three reusable architectural decisions in this design space: the decision for the type of DSL development process, the decision for the concrete syntax style, and the decision for developing an external vs. an embedded DSL. These decisions are foundational for each DSL project. Each of these decisions has a number of (candidate) patterns for DSL design. These (candidate) patterns define alternative solutions in the shared context and problem space of the respective reusable architectural decision. 1