I travel to the Middle East, I travel to China, I travel to Europe. It's all very rewarding - the only problem is the travel is getting more and more difficult for me now. Ten years ago I would have enjoyed it a lot more.

Many of the projects I'm most proud of are tall buildings, especially the housing projects. In New York I have two: one in Kips Bay and one at New York University. At that time, those projects were most challenging.

Success is a collection of problems solved.

I haven't taken any new projects in the past years - I told myself, if I cannot live long enough to finish it, I don't want it.

On a daily basis, my home life is very simple. I spend about 2 hours every morning reading the newspaper. As my two assistants will tell you, I don't come to work in the mornings, for two reasons. First, I want to be informed - that means I go through The New York Times every day, and then I watch some news on television. The second is, mornings are the best time to communicate with my clients abroad.

When I got the opportunity to do the new wing [the Schauhaus] for the German Historical Museum, for instance, I didn't see it as an opportunity for my own ego, to do something so exciting that every architectural publication would want to put it on the cover. I accepted it because I knew it was going to be a very difficult project, and I wasn't sure I could do something exciting there.

Luxembourg was and still is today a crossroads, the place where Germany meets the rest of Europe. The country lost part of its territory to Belgium in the 1800s, and during World Wars I and II the German military overran it. Very few people have visited Luxembourg - when I went there and looked at it, I said, my God, it's built on a rock. And within the rock they had a castle, and within the city there's a network of tunnels so the residents could move around and defend themselves. That was of great interest to me.