Dense and mixed land-use configurations are assumed to encourage high and prolonged activity levels, which in turn are considered to be important for the condition of urban neighbourhoods. We used mobile phone usage data recorded in Amsterdam, the Netherlands, as a proxy for urban activity to test whether the density in different forms of urban land use increases the level of activity in urban areas, and whether mixed land uses can prolong high levels of activity in an area. Our results indicate that higher densities correspond with higher activity levels, mixed land uses do indeed diversify urban activity dynamics and colocating particular land uses prolongs high activity levels in the evening hours. We proceed to demonstrate that mixed activity provisions and high urban activity levels coincide with urban neighbourhoods that are considered attractive places in which to live and work, while lower activity levels and markedly low activity mixes coincide with neighbourhoods that are considered disadvantaged.