The NYU Stern Urbanization Project has been organizing a number of great seminars that cover interesting speakers at the intersection of urban planning and economics (Check their YouTube channel here). In December last year, they had Edward Glaeser talking about Cities, Development, and Density.
In case you want a more academic reference, much of Glaeser's presentation is present in his recent paper on 'the causes and consequences of urbanization in poorer countries'.
