Complex sentence: Gu's original no longer exist, the painting is survived in a 12th century remake (see below) of the subsequent Song Dynasty (960--1279); the painting is housed in the Palace Museum in Beijing.
Split into simpler sentences: Gu's original no longer exists, but the painting survives as a 12th century remake during the subsequent Song Dynasty (960--1279). Tthe painting is housed in the Palace Museum in Beijing.