90° corner bends and waveguide crossings have been investigated in order to increase the integration density of multimode polymer waveguide devices. Using a platform consisting of polymer waveguide cores surrounded by glass and PMMA (polymethylmetacrylate, a clear plastic) as lower and upper cladding, respectively, and air at the sides, it is shown that these components can increase the integration density by a considerable factor with negligible loss penalty. Waveguide crossings have been studied experimentally, and for crossing angles above 35° the excess loss is below 0.15 dB and no excess loss could be measured for a 90° crossing. 90° corner bends have been designed and measured to have very low losses of 0.2 dB over a wide wavelength span. The influence of the waveguide width on the 90° corner bend loss has been characterized and an optimal width has been identified.