Urban design is about providing an infrastructure for its inhabitants. An important consideration of design is to provide natural outdoor conditions that are pleasant and conductive to human activities. A well designed outdoor urban environment will also make the design of individual buildings within it easier. There are many design parameters, for example: Development Density, Plot ratio, Site Coverage, Skyline, Building to Space Ratio, Permeability, Building Shapes and so on. This paper reports a study based on “skylines” as a design parameter, and how it affects daylight and natural ventilation provisions and performance. Experiments are conducted with physical models in artificial sky, as well as using computational lighting simulations. The study establishes that by varying the skylines of the city, the overall daylight performances could be improved when compared to a city with a uniform skyline - given the same density. The message of the paper is that: through better understanding and design, high density cities could be planned and optimised without losing the development efficacy of the land.