Acheng is a city in the north-east of China. Officially merged with the large neighbouring city of Harbin, it's known for the remains of a historical walled city, just outside the current city centre.
The main sight is located just a few km south of Acheng centre. Here, you'll find the ruins of Huining Fu, the capital of the 12th century Jin dynasty. It's been declared a national historic reserve, and apart from the ruined city walls there's a museum on the site as well.
There is also a Waterpark outside of the city.