Tangible Windows are a novel concept for interacting with virtual 3D information spaces in a workbench-like multi-display environment. They allow for performing common 3D interaction tasks in a more accessible manner by combining principles of tangible interaction, head-coupled perspective, and multi-touch techniques. Tangible Windows unify the interaction and representation space in a single device. They either act as physical peepholes into a virtual 3D world or as physical containers for parts of that world and are well-suited for the collaborative exploration and manipulation of such information spaces. One important feature of Tangible Windows is that the use of obtrusive hardware, such as HMDs, is strictly avoided. Instead, lightweight paper-based displays are used. We present different techniques for canonical 3D interaction tasks such as viewport control or object selection and manipulation, based on the combination of independent input modalities. We tested these techniques on a self-developed prototype system and received promising early user feedback.