SJ wrote:Hervé wrote:ok ok there are some slight variations, but none has harsh shadows...

Yeah, that's a thing I'm always looking for... Some good HDRI-Maps of only skies with clear, bright sun that's creating harsh shadows. Found none so far. I guess the reason is, the cameras don't "like" to be exposed directly toward the sun with not the slightest cloud covering it.
@Jan Häusle: would that be possible to make? I mean, surely it would be a bestseller among architects

Do you have PhotoshopCS2? Sorry Jan, I'm going to give SJ a tip, but it will cost money.
Go to
http://www.1000skies.com/fullpanos/index.html and buy a few of their high-rez panos then convert them to 32-bit radiance files with Photoshop While not TRUE HDRIs, you can fake it a bit by playing with gamma and exposure settings and blending you own multiple exposures.
You are still better off with Jan's work.
They will work quite well.