Indoor navigation and localization are challenging due to the limits of available devices. A number of devices, such as GPS [3], beacons [5], infrared positioning system, ultrasonic positioning system and RF positioning system [21] have been explored. We propose to utilize the latest mixed-reality technologies to achieve indoor localization and navigation functions.In this thesis, we propose a cross-platform system for navigating indoor environments using Microsoft HoloLens and iOS devices. Our approach leverages on device sensors and Vuforia API of image marker to localize users inside a building. The user locations are further synchronized among all devices connected through the interface of Unity net- working, which is scalable and reusable for both HoloLens and iOS platforms. We provide both individual view version and server version for different purposes, both visualizing user locations in real-time when users are connected through HoloLens or iOS devices. We develop several different designs for visualizing 3D building model, so that users can choose them flexibly according to their exploration tasks. While isometric visualization provides complete structural information of building in 3D, staircase visualization reduces occlusions from isometric view by arranging floor in a staircase fashion. Additionally, or- thographic visualization provides top view of all the floors. We also added immersive view which enhances navigation by providing augmented visualization for mobile devices.We have conducted a set of small user studies covering different use cases of the project including building navigation, friend finder and rescue operation. Users were given differ-ent devices and were asked to switch between different visualizations as they performed the tasks. We also obtained an expert feedback from psychology professor. Results have demonstrated promising results for this technique for everyday building navigation and emergency situations.