I used "SketchUp Make 2017" and the extension called "Bitmap to Mesh".

I got the greyscale gradient from tangrams heightmapper.

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And I did the aligning phase using the lines of the streets from tangram's site and a "first stage" taken from Iberpix to get where the medieval fort was placed:

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When setting the X to Z scale, I used the number that tangram's site provides.