In common parlance, it is the architect who builds. However, racetracks require civil engineering with roads as well as structural engineering. We have about as many architects as civil engineers working for us. In our office, the lines are blurred: I mingle with architecture, and my partner Peter Wahl, who is an architect, has a say in civil engineering.

I’ve been racing since I was 18, the first races in my mother’s car – she didn’t know anything about it. I was infected by this sport. After the first hillclimbs there were various series on circuits. Eventually I drove in the European Touring Car Championship and part of the World Championship. Later I went to the Nordschleife of the Nürburgring. One of the reasons I became self-employed was to have enough time for driving. At the same time, I tried to have something to do with the tracks at a work-related level as well.

With very small planning tasks, for example the rerouting of an escape route or the construction of a pit wall. That’s how I got my foot in the door of motorsport design. At some point people said, “Tilke is an expert.” Then came the first two commissions for completely new racetracks: the Sachsenring and the Österreichring, now the Red Bull Ring, in Spielberg.

Both. Investors and operators approach us – we also work on existing routes again and again. In addition, we always stay on top of things ourselves and look for commissions or participation in competitions.

We are not currently working on a Formula 1 circuit. Last year, however, we were working on the Baku City Circuit in Azerbaijan, a Formula 1 street circuit that runs directly through the old town of Azerbaijan, which is a UNESCO heritage site. Currently, we are working on several private circuits, a larger one in Kuwait – large in the sense of an elaborate infrastructure that could possibly be used for Formula 1 one day – and several smaller circuits in Vancouver, Morocco, China and Indonesia.

First, we illuminate the property. What is the topography of the site, i.e. the spatial structure and the earth’s surface? What are the external traffic flows? Once all the relevant data has been gathered, we start planning the route – and always in the same way: With a thick pencil, we sketch around on a map and first of all determine the start and finish line. Where these are located depends very much on the associated facilities such as the pit building, paddock or media centre. After that, we take the planning to the computer and into the simulation programme. Sometimes we have to realise that things don’t work the way we imagined. Then we have to rethink or start from scratch.

There are safety requirements set by the FIA and target track lengths and sections set by the developers or investors. They want to have a particularly exciting track or they have to stick to a certain budget. Both are a challenge. Both are very interesting.

The BILSTER BERG was a very exciting project for us because the terrain has such an insanely great topography. The BILSTER BERG is a unique track in terms of the sequences of curves. That made the job very interesting for us. In the end, something like a natural circuit was created at BILSTER BERG. The difference in altitude along the entire length is 72 meters, the biggest gradient is 26 per cent, and the second biggest gradient is 21 per cent. In total, there are over 40 troughs and crests, as well as nine right-hand and ten left-hand curves. That is extraordinary.

I was surprised at how difficult it is to drive. The race track is absolutely thrilling.

I would like to build a race track that goes through the mountains, that is, through really rugged terrain. Or through a city like New York.

That’s incredibly difficult to say, the Nordschleife is, of course, unique among the older tracks. I have driven hundreds of races there. Among the new tracks, I actually like the BILSTER BERG the best simply because it’s a special challenge for the drivers.