Another expedition in Central Asia followed in 1899-1902 through the Tarim Basin, Tibet and Kashmir to Calcutta. Hedin navigated the Yarkand, Tarim and Kaidu  rivers and found the dry riverbed of the Kum-darja as well as the dried out lake bed of Lop Nur. Near Lop Nur, he discovered the ruins of the 340 by 310 metres (1,120 by 1,020 ft) former walled royal city and later Chinese garrison town of Loulan, containing the brick building of the Chinese military commander, a stupa, and 19 dwellings built of poplar wood. He also found a wooden wheel from a horse-drawn cart (called an arabas) as well as several hundred documents written on wood, paper and silk in the Kharosthi script. These provided information about the history of the city of Loulan, which had once been located on the shores of Lop Nur but had been abandoned around the year 330 CE because the lake had dried out, depriving the inhabitants of drinking water.
During his travels in 1900 and 1901 he attempted in vain to reach the city of Lhasa, which was forbidden to Europeans. He continued to Leh, in Ladakh district, India. From Leh, Hedin’s route took him to Lahore, Delhi, Agra, Lucknow, Benares to Calcutta, meeting there with George Nathaniel Curzon, England’s then Viceroy to India.
This expedition resulted in 1,149 pages of maps, on which Hedin depicted newly discovered lands. He was the first to describe yardang formations in the Lop Desert.