By Vo Thanh  March 17, 2019 | 04:36 pm GMT+7 The wall of the gate into Hue’s former imperial city is infected with moss and fungi. Photo by Shutterstock An ornate gate in Vietnam’s former imperial citadel is being cleansed of moss, fungi and lichen with German assistance. On Friday the Hue Monuments Conservation Center and German company Karcher, which specializes in cleaning technology and equipment, began to clean the Meridian Gate using high-pressure steam. The steam cleaning at a temperature of 100 degrees Celsius is expected to remove all kinds of dirt and biological contaminants on and under the surface, including inside small cracks. The work is headed by Thorsten Marco Mowes, an expert in cleaning and sanitation technology, and Andrea Teufel, a conservation expert. The work is sponsored by the company. The citadel is a part of Hue’s Complex of Monuments, a UNESCO world heritage site since 1993. It has many relics from the era of the Nguyen Dynasty, the last feudal rulers of Vietnam, and is among the top historical and tourism sites in the country.