Tables have historically played a key role in many real-time collaborative environments, often referred to as "war rooms". Today, these environments have been transformed by computational technology into spaces with large vertical displays surrounded by numerous desktop computers. However, despite significant research activity in the area of tabletop computing, very little is known about how to best integrate a digital tabletop into these multi-surface environments. In this paper, we identify various design requirements for the implementation of a system intended to support such an environment. We then present a set of designs that demonstrate how an interactive tabletop can be used in a real-time operations center to facilitate collaborative situation-assessment and decision-making. Categories and Subject Descriptors H.5.2 [User Interfaces]: Interaction styles General Terms Design, Experimentation, Human Factors. Keywords Tabletop interaction, interactive spaces, groupware,...