We report on a polymer-based planar lightwave circuit platform that enables high levels of integration. The materials used represent the state of the art in optical polymers, and include properties such as ultra-low loss (0.1 dB/cm in single-mode waveguides at 1550 nm), widely tunable refractive index contrast (0-35%), and large thermo-optic coefficient (-3.2×10-4/°C). The large index contrast values enable compact photonic microcircuits. The circuits are produced photolithographically, and can have a variety of inorganic materials integrated in them (e.g., by insertion in slots or by flip-chip mounting), resulting in a platform that can support functions that span the range of the building blocks needed in optical circuitry, while using the highest-performance material for each function. In this manuscript, we focus on the polymeric microcircuits, which provide interconnects, static routing elements such as couplers, taps, and multi/demultiplexers, as well as thermo-optically dynamic elements such as tunable couplers, switches, variable optical attenuators, and tunable notch filters. We demonstrate complex-functionality polymeric photonic microcircuits based on this technology, including fully reconfigurable optical add/drop multiplexing subsystems on a chip that perform channel switching, power monitoring, load balancing, and wavelength shuffling.