I think that Walter De Maria's Lightning Field, Michael Heizer's City, and Charles Ross's work in Star Axis New Mexico , all three will last for a millennium.

I remember when I went to a gallery in Paris at one point, they had drawings of earthworks set in different places. I asked the person sitting at the gallery desk where these works were - where in France they could be found. She looked at me in horror as if I'd asked something completely insane. She said, "Well, of course, these works don't actually exist. They're concepts."

I enjoyed cross-country road trips. And I found the work challenging because it was art that existed on the land rather than mere concepts in a gallery or photographic documentation, or any of the paraphernalia that can be used to indicate that. The art was on the land.

I think the four land artists I showed all worked within a few years of each other. And they were standard bearers, I suppose, for land art. They each did very separate things. Apparently, later in California, a lot of artists started working in that medium and there was something of a rush of earthworks. But I wasn't involved with that.

I think that Walter De Maria's Lightning Field, Michael Heizer's City, and Charles Ross's work in Star Axis New Mexico , all three will last for a millennium.

I opened with Edward Kienholz's The Beanery, and that's such a controversial piece that I think that brought people right away. It was a room-size work that one walked into. It was a bar with Kienholz-type figures sitting and drinking and talking - all life-size characters in a life-size setting. The exhibition was covered in Time, Newsweek, and Life, so it had huge recognition right away.

I myself had lived in the San Fernando Valley many years ago, when it was a much wilder place, and we used to go walking in the wild areas. So that early experience had a lot of similarities for me to the places that Double Negative was being done.