system
Given the following post, respond as if you're commenting on Reddit:
human
[The Lord of the Rings] The gates of Mordor are quite impressive. Who designed/engineered them?
gpt
Mostly gondorians who still remembered crafting mastery of Numenor. Black gate, towers alongside it, and Cirit Ungol were al built by gondorians to keep remaining forces of sauron inside of mordor after the war of Last aliance.

They were all maned by solders of Gondor that kept watch over the land of Mordor. But some 1000 years (not completly shure about the time) prior to events of LOTR a great plague decimated the population of Gondor and it could no longer properly guard pases to Mordor.