Yian-Ho is a fictional city mentioned in "The Diary of Alonzo Typer", by H. P. Lovecraft and William Lumley, and again in "Through the Gates of the Silver Key", by H. P. Lovecraft and E. Hoffmann Price.
Description[]
Yian-Ho is described as a "shunned", "dreaded" and "abhorred" place, identified as "that lost and hidden city wherein brood aeon-old secrets, and of which dim memories older than the body lurk behind the minds of all men". Claes van der Heyl claims to have been to Yian-Ho "in the veritable flesh of this body, as none other among the living has been", and there learned the means to summon a monstrous tentacled entity. (HPL: "The Diary of Alonzo Typer")
A clairvoyant Yogi that Harley Warren was acquainted with also claimed "that he alone of living men had been to Yian-Ho". The Swami Chandraputra described Yian-Ho as "the hidden legacy of sinister, aeon-old Leng". (HPL: "Through the Gates of the Silver Key")
Behind the Mythos[]
It's not known whether Yian-Ho is related to (or even synonymous with) the mystical city of Yian, mentioned in Robert W. Chambers' "The Maker of Moons" and H. P. Lovecraft's The Whisperer in Darkness.