Tanelorn is one of the eternal cities of
Law. While it is unclear where these cities hide today, on the dead earth in
Michael Moorcock's
Dancers at the End of Time Tanelorn and
Shanelorm are mentioned.
It is notable that these cities apparently survived even the annihilation of the New World of Law that replaced the previous world at the end of Eternal Champion. Maybe they hitchhiked on Stormbringer.