Accurate and real-time positioning is highly demanded by location-based services in 5G networks, which are currently being standardized and developed to achieve significant performance improvement over existing cellular networks. In 5G networks, many new envisioned technologies, for example, massive Multiple Input Multiple Output (MIMO), millimeter Wave (mmWave) communication, ultra dense network (UDN), and device-to-device (D2D) communication, are introduced to not only enhance communication performance but also offer the possibility to increase positioning accuracy. In this article, we provide an extensive overview of positioning architectures in previous generations of cellular networks to show a road map of how positioning technologies have evolved in past decades. With this insight, we then propose a general positioning architecture for 5G networks, by exploiting the new features of emerging technologies wherein. We also investigate positioning technologies that have great potential in achieving sub-meter accuracy in 5G networks, and discuss some of the new challenges and open issues.