This paper presents the motivation, design, and a preliminary evaluation of a virtual world builder, CLOVES. CLOVES is designed to support rapid construction of data-rich virtual environments and instruments for young children's science inquiry learning. It provides a layered programming interface such as a visual design environment, scripting layer, and low-level application programming interface targeting for multiple levels of programming expertise. It is also intended to be a collaborative medium among interdisciplinary domain experts such as educators, modelers and software developers. A case study was conducted to evaluate the capabilities and effectiveness of CLOVES. The results showed that designers actively participated in decision making at every stage of the design process and shared knowledge among one another.