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What was happening at the Nurburgring on 25-27 August?
I'm not sure who's likely to know this, but I'll give it a go.

From 18-31 August I was on holiday driving around Europe, on the 25th we were meant to be going toward Stuttgart, but I noticed on the map that we could make a very small detour and visit the 'Ring. We parked in one of the car parks and I could instantly tell that there was something going on, the cars were too loud to be public. I went to ask if there was somewhere we could see the track from, and was told that it was the testing day for a race weekend, and we'd have to buy a ticket. Screw that, we went to find some food, and it just so happens that not only does the cafe have a view of the start/finish straight, but it has an outside stand that you can sit in and watch the cars go by. We stayed for about half an hour, then headed off.

It looks like a great circuit, I'm definitely going to head back in future for a longer look (and a drive round). It's very unnerving to be on a public road, and see cars fly past at 150+mph on the other side of a hedge.

The cars seemed to be a complete mixture. From old and new Porsches and tuned up BMWs and Mercs to Jap cars like NSXs and S2000s, there was even a Vauxhall (Opel) Zafira going round! Couldn't tell if they were on the large or small circuit, I'm afraid.
#2 - ajp71
^^ Well by large or small I assume your meaning they were on one of the current GP circuit loops, in which case it may well have just been a general test session. If the cars passing you on the road parallel to the straight were competition cars then it was a test session for the 24 Hour race (although it's perfectly possible there was a test on the GP track and public lapping on the Nordshleife.
#3 - Vain
That should have been a testing for the 6 hours ADAC Ruhr Cup race on the 26th (GP + Nordschleife).
That's a race in the BF Goodrich Endurance Championship (VLN).
The site for that league is only available in german, though. Here are some pictures. (Still, german text around it, but pictures don't have text.)

Vain
Thanks.

Vain, those were the cars I saw. Any news on where the Zafira came ?

FGED GREDG RDFGDR GSFDG