Well, just northwest of Birmingham was an area called the Black Country, so called because it had been marred with pollution from all the coal mines, iron foundries and steel mills dotting its landscape thanks to the Industrial Revolution. The air was so dense with smog and dust and ore that the whole place looked like Godzilla's shithouse, all the time:
There's definitely a troll under that big wheel on the left.
So, when it came time for Tolkien to create a homeland for the most evil being in his fantasy world, he just channeled the Black Country into his writing, renaming it "Mordor" because that sounded less like a racist old debutante's description of Africa.
For a while, Tolkien lived with his aunt in a section of Birmingham called Edgbaston -- an area that was known for having two very distinct towers in it: