One of the biggest and most persistent challenges in contemporary ecology is to explain the high diversity in ecological communities such as tropical forests, grasslands, coral reefs, or plankton ecosystems. The broad objective of our project is to understand the relative importance of processes and factors that govern the composition and dynamics of species-rich communities. Advances in this issue have important implications for efforts to protect terrestrial biodiversity from climate and land use change. Surprisingly, although most processes which are thought to contribute to species coexistence have a strong spatial component, the rich source of information on spatial patterns has not been used. To accomplish our goal, we take a radically different approach than previous attempts and adopt a spatially explicit perspective that will allow us to take significant steps towards a Unified Spatial Theory of Biodiversity. We use the best data sets available, i.e., 25-50 ha mega-plots of tropical forests each comprising several hundred of species and >100000 trees that are monitored and censuses every 5 years. We proceed in three steps. (1) We quantify the highly complex spatial structures found in these forests using state-of-the-art techniques in spatial pattern analysis. (2) We build a range of individual-based spatially-explicit simulation models ranging from pure neutral models to detailed process-based models of tropical forest, such as FORMIND. (3) We use pattern-oriented modelling to confront these simulation models with the set of patterns identified in (1) to identify the most parsimonious models that account simultaneously for all (spatial) patterns. We anticipate that the new spatial perspective and innovative computer modelling techniques will allow for a major break through in this important challenge at the frontier of ecological research, and open up new horizons for understanding and conservation of biodiversity.