The Barad Dur Is A Prefab

[fatclown]

I was going over the Tale of Years this evening, looking for information for a different article, when I came across an unexpected puzzle.

In the Tale of Years for the Second Age (Return of the King p. 364 hardback), it states the following:

"c. 1000 Sauron ... chooses Mordor as a land to make into a stronghold. He begins the building of Barad-dur.
. . .
"c. 1600 Sauron forges the One Ring in Orodruin. He completes the Barad-dur. Celebrimbor perceives the designs of Sauron..."
What makes this curious is the clear statement given by Elrond about the Dark Tower's construction, as he described the cleaning-up after the Battle of the Last Alliance (Fellowship of the Ring p. 257 hardback, emphasis mine):
"The Dark Tower was broken, but its foundations were not removed; for they were made with the power of the Ring..."
Now since the Ring wasn't forged until SA 1600, this means that Sauron spent approximately six hundred years building the Barad-dur... before he had built the foundation! Moreover, once the foundation was finally laid, the Barad-dur was completed almost immediately!

...How do we explain this? How can we explain how Sauron - a Maia of Aule, no less - could spend six hundred years building a Tower, and yet build the foundation last?

Doubtless there are many possible explanations; I'm looking forward to hearing what others may suggest. For my part I've been thinking about it all evening, and I believe I have a possible answer - one clearly in character for Sauron, the master of cruelty and deceit:

Pre-fabricated modular housing.

Sauron developed the black and heinous art of building mobile homes.

...It's worth observing that, once Sauron had the foundations set up, he could also rebuild the Barad-dur with incredible speed. The Tower was "levelled to the ground" at the end of the Second Age (Silmarillion p. 294 hardback); yet, according to the Tale of Years, Sauron began rebuilding the Barad-dur in TA 2951 - and it was evidently finished by the time of the War of the Ring (TA 3018), only some 67 years later! More evidence in favor of the Barad-dur being a prefab, don't you think?

Perhaps the most convincing evidence, however, comes from none other than the Mouth of Sauron (Return of the King p. 166 hardback) when he implies that just having to live in the Barad-dur constitutes an unimaginable torture. It's also worth noting that, on the same page, he notes that he himself has plans to move to Isengard at the first available opportunity.