Pyramids

Are there Pyramids (or something similar) somewhere to be found on Middle-Earth. As far as I know Tolkien's work, I don't recall any mention of structures like Pyramids. If a Narrator was to place some, they should maybe be dropped in the South or East in the territories that weren't covered by the books.

What would you say?

I could see the Ziggurats of old poping up among the haradrim and some Easterling kindgoms.

It's been a while since I read anything about Numenor, but IIRC, there was a reference or two that said some of the later Numenorean kings built huge tombs for themselves. I would assume they'd be something similar to the tombs in Minas Tirith, possibly on a much larger scale.

But that probably won't do your campaign much good unless you want to send your party exploring underwater.