博大精深 | bó dà jīng shēn
Xi Jinping used this chengyu during a visit to the Dunhuang Research Academy on January 31st, 2020.
Meaning
Wide-ranging and profound, broad and deep.
Original
“敦煌文化集建筑艺术、彩塑艺术、壁画艺术、佛教文化于一身，历史底蕴雄浑厚重，文化内涵博大精深，艺术形象美轮美奂，给我留下了很深的印象。”
Source
http://www.xinhuanet.com/politics/leaders/2020-01/31/c_1125516300.htm