The LH Urban Digital Twin Platform is a comprehensive solution for new town planning and development that utilizes open source digital twin technology. The platform combines real-world data with spatial information context to offer a three-dimensional sharing/collaboration integration support system. Developers will appreciate the platform's flexibility and scalability, which are based on a microservice architecture that connects multiple modules independently and loosely. The platform utilizes open standards WMS, WFS, WCS, WPS OGC Web Service standard features through GeoServer and GeoWebCache, a tile cache server that accelerates map delivery built into GeoServer. Additionally, the platform supports visualization of data in various formats using mago3D, F4DConverter, and Smart Tiling. The platform offers a range of services, including automatic apartment building placement, construction site safety management, 3D urban landscape simulation, environmental planning simulation, and underground facility visualization simulation. The platform also features real-time monitoring and visualization of IoT-based data, which is of particular interest to developers interested in smart city development. Firstly, the presentation will show how open source based digital twin visualize the complex 3D city models in a web browser. Secondly it will showcase the platform's features and data, including actual system's functions and service UI/UX through a video. Attendees will gain insights into how the platform can be used to support rational decision making during complex urban planning, design, development, and operation stages.