The Yuan Ming Yuan (Garden of Perfect Brightness) started construction on 1707, in the 46th year of the Kangxi reign.
It was built for his 4th son, the future Yongzheng.
It served as a place of residence for 5 Emperors including Qianlong. Sadly, it was ransacked by British and French troops in 1860 as part of their revenge for the Boxer Rebellion.
Re-reading these 2 excellent books bring back fond memories of my visit to Peking to see the ruins.