How about Heilongtankeng in She Yan?

She Yan Black Dragon Pool Pit is good. According to China Antique Network, the Black Dragon Pool Pit in She Yan is hard, delicate and moist as jade. There is a clear metallic sound when knocking, and water storage is not consumed. It's cold and icy, its breath can be studied, and its ink is like oil, which is harmless. Carefully carved, simple and generous. It has natural texture, diverse and unique texture, and has been praised by calligraphers of all ages.