For 10 points, name this region in China, located between Russia and North Korea, which has an English name that derives from an ethnic group native to it.
To discourage migration into this geographical region, a ditch and embankment planted with willows called the Willow Palisade was constructed. This region has a historical name meaning "east of the pass," referring to the Shānhǎi Pass, an entry point into this region. Part of this region was ceded in the Treaty of Aigun, and this region's northern border was set in the Treaty of (*) Nerchinsk. A Neo-Byzantine Saint Sophia Cathedral was constructed by Russians in this region's city of Harbin. A border between this region and a foreign country to its south is the site of Mount Paektu and is marked by the Yālǜ River. For 10 points, name this region in China, located between Russia and North Korea, which has an English name that derives from an ethnic group native to it.
To discourage migration into this geographical region, a ditch and embankment planted with willows called the Willow Palisade was constructed.
Manchuria [or Mǎnzhōu; accept Dōngběi or Northeast China; accept Guāndōng] (Dongbei means "Northeast.")