From TLI Networks:
Skyscraper is a fully-featured, modular, 3D realtime building simulator, powered by the Scalable Building Simulator (SBS) engine. The main feature SBS provides is a very elaborate and realistic elevator simulator, but also simulates general building features such as walls, floors, stairs, shaftwork and more. Many more things are planned, including gaming support (single and network multiplayer), and a graphical building designer. Skyscraper is written in C++ and uses the OGRE graphics engine, Bullet for collisions/physics, Caelum for dynamic sky, FMOD for sound, the wxWidgets GUI library, and is multiplatform. The current versions aim for a future 2.0 release.