In this talk I will consider an aggregation model with nonlinear diffusion in domains with boundaries and present on the zero diffusion limit of its solutions. This model is used in describing phenomena related swarming and social aggregations, such as biological swarms and pattern formation, granular media, and self-assembly of nanoparticles. Using the formulation of the aggregation model as a gradient flow on spaces of probability measures equipped with the Wasserstein metric, I will present the convergence of weak solutions for fixed times, as well as the convergence of energy minimizers in this limit. I will also present numerical simulations that support the analytical results and demonstrates that adding small nonlinear diffusion approximates, as well as regularizes, the plain aggregation model.