Episode 16 of The Trigan Empire
The Lost City
aka De verboden stad (Dutch title)
The Forbidden City (Dutch title, translated)
Written by Mike Butterworth
Illustrated by Don Lawrence
The Lost City was originally published in 12 instalments in issues 371 (22 February 1969) to 382 (10 May 1969) of Look and Learn magazine.
It was reprinted in 1976 in 3 issues (3 January 1976—17 January 1976) of Vulcan comic.
It was reprinted in 12 instalments in issues 866 (19 August 1978) to 877 (4 November 1978) of Look and Learn magazine.
It is reprinted in Volume 5 of The Trigan Empire—The Collection (the Don Lawrence Collection).
It is reprinted in Volume 2 of The Rise and Fall of the Trigan Empire (Rebellion).
Plot summary (Dutch)
MediaFire via British Comics Compilations