As technology scales, interconnects dominate the performance and power behavior of deep submicron designs. Three-dimensional integrated circuits (3D ICs) have been proposed as a way to mitigate the interconnect challenges. In this paper, we explore the architectural design of cache memories using 3D circuits. We present a delay and energy model, 3DCacti, to explore different 3D design options of partitioning a cache. The tool allows partitioning of the cache across different device layers at various levels of granularity. The tool has been validated by comparing its results with those obtained from circuit simulation of custom 3D layouts. We also explore the effects of various cache partitioning parameters and 3D technology parameters on delay and energy to demonstrate the utility of the tool.