The growth of the Internet of Things (IoT) results in a proliferation of different protocols (ZigBee, Bluetooth, 6LowPAN, Z-Wave, Wi-Fi, etc.). Organizations tend to quickly deploy several IoT applications over time and thus face heterogeneous IoT systems, combining different IoT protocols in different places of the overall system. This heterogeneity of protocols makes these networks hard to monitor or control, and some misconfigurations or unexpected device behaviours may even expose users to security issues. In this work, we propose IoTMap. IoTMap provides an iterative graph-based modelling of interconnected IoT with a multi-layers view ranging from point-to-point transmissions to application-type analysis. With this modelling, we aim to highlight the network state at a specific time. It can also be used as the intelligence gathering phase during a penetration testing to evaluate the global network security.