In this paper, we introduce the K-Culture Time Machine Project, which develops a mobile AR platform for visualizing time-space connected cultural contents of Korea. Existing AR Applications in cultural heritage domains are currently not interoperable and cannot reuse content. To solve this problem, we developed the modified AR reference model as generic framework of a context-aware AR platform; and we developed the context-aware AR platform with several core technologies according to this model. For back-end, we established the Korean Cultural Heritage Data Model (KCHDM) to aggregate the heterogeneous cultural heritage databases in Korea. We also developed the semi-auto time-space correlation generation module for domain experts. Moreover, we developed the authoring tool to generate the time-space connected AR contents. For the front-end, we developed the vision- and sensor-based spatial data composition technology to perform the solid tracking in outdoor environment and context-aware AR framework. Through the UI/UX and 3D contents, whole technologies are packaged into the mobile AR platform. As a validation process for the application, a mobile AR application for the Korean world cultural heritage was developed. Based on this project, an interoperable AR platform that responds with heterogeneous database would be developed and smart tour guide of the cultural heritage site would be possible.