Complex sentence: It is one of the "Five Grand Palaces" built by the kings of the Joseon Dynasty and because of its location east of Gyeongbok Palace, Changdeokgung, with Changgyeonggung, is also referred to as the East Palace (東闕, "Donggwol").
Split into simpler sentences: It is one of the "Five Grand Palaces" built by the kings of the Joseon Dynasty. Because of its location east of Gyeongbok Palace, Changdeokgung, with Changgyeonggung, is also referred to as the East Palace (東闕, "Donggwol").