Radiative cooling is an emerging sustainable technology that does not require electricity to function. However, to realize sub-ambient cooling, the effects of the undesired incident solar energy must be minimized. Considering an ideal blackbody radiator at 300 K, the maximum cooling power density is 160 W/m2. Here, we report an architecture capable of overcoming this challenge by using two spectrally selective mirrors to simultaneously absorb the incident sunlight and re-direct the thermal emission from a vertically aligned emitter. With this configuration, both sides of the vertical emitter can be used together to realize a measured local cooling power density of over 270 W/m2 in a controlled laboratory environment. Under standard atmospheric pressure, we realized cooling that was 14C below the ambient temperature in the laboratory environment and a more than 12C temperature reduction in outdoor testing.