Gas transmission pipelines crossing rivers and natural obstacles are installed using the trenchless HDD technique (Horizontal Directional Drilling) increasingly. Nowadays, the state-of-the-art HDD technique permits to install pipelines over distances greater than 1,800 m. However, this has not yet been implemented for pipelines with an outside diameter of up to 56’’. The project of a trenchless river crossing near the Turkmen city of Karabekaul installing a 56’’ gas pipeline towards China underneath the Amu Darya River offered exactly such a challenge. Besides the drilling execution, the project planning and preparation were the special engineering challenges. Prior to this extraordinary project, extensive examinations and plannings led to unusual measures for site facilities, execution and equipment to be applied. Among other things, special solutions regarding risk assessment during pipe insertion, drilling plant configuration and overbend construction were found and successfully implemented. In addition to the technical and local conditions, the tight schedule affected the planning and the choice of the equipment. The engineering, production and mobilization of the equipment preceded the technical implementation during a 2.5-month planning phase. The technical execution of the project installing the 56’’ carrier pipe and the conduits running in parallel took 6 months and was finished successfully in February 2010. The successful execution has expanded the limits of the applied HDD technique regarding feasible pipeline size and length. The project experience will allow for a differentiated approach for future large-scale projects regarding trenchless technology.