This document discusses recent approaches to spatial interfaces. It identifies three main approaches: 1) Materialization of an alternative world using optical, acoustic, and haptic techniques, 2) Extension of spatial information and cognition by utilizing hidden information and changing perspectives, and 3) Improvement of real-world values such as pedestrian traffic control. Several examples are provided for each approach, including CAVE, IllumiRoom, Oculus Rift, and systems that simulate acoustics, add augmented surfaces, or control pedestrian flow.