Why has this NYC apartment in a prime location been filled with 140 tons of dirt for forty years?

Why is it that for forty years, a large apartment located in New York City's pricey Soho neighborhood has been filled with 140 tons of dirt? The answer is… art. Located at 141 Wooster Street, the New York Earth Room was created by artist Walter De Maria in 1977 on a commission from the Dia Art Foundation who still own the real estate. It was the third of De Maria's earth rooms but the prior two, in Germany, no longer exist. Yes, you can visit the New York Earth Room but you're not permitted to walk on the soil, touch it, or even take photos. The room has a caretaker who ensures that it is raked, occasionally watered, and that any mushrooms are yanked. From Oddity Central:

Bill Dilworth, the room's caretaker, has been answering visitors' questions since 1989. He spends his days sitting at a desk, counting visitors, answering queries, and looking mysterious. Just don't ask him what the message Walter De Maria wanted to convey is.

"People always wonder what it means, but the artist never attached any meaning to it," Dilworth, an artist himself, told Gothamist. "So I think what I really want people to know is that they don't have to know anything about the work."

Atlas Obscura claims that the New York Earth Room is estimated to be worth at least a million dollars, which sounds like a lot, but is actually modest compared to the price of the space it takes up.

image: Google Maps