Situated eight kms to the East of downtown Kathmandu, Boudhanath Stupa is one of the most important landmarks in Kathmandu, visible as soon as one lands at the Tribhuvan International Airport. It is the largest stupa in the Kathmandu Valley. The 36-metre-high stupa of Boudhanath is also one of the largest stupas in South Asia. Surrounded by numerous monasteries, Boudhanath is the centre of Tibetan Buddhism in Nepal. The stupa is built in the shape of a Mandala, designed to replicate the Gyangtse of Tibet. The structure was once on the ancient trade route to Tibet and it was here that Tibetan merchants rested and offered prayers for centuries.