Ring a nondescript buzzer and ascend far above the streets to a quiet, meditative room filled entirely with dirt. Here, 3,600 square feet of floor space is covered with 280,000 pounds of earth. One of only three of De Maria's Earth Rooms still in existence, the installation has been open to the public, for free, since 1980, commissioned and maintained by the Dia Art Foundation. Bill Dilworth, the room's caretaker for the past three decades, waters and rakes the dirt once a week, stirring the distinct and sharp loamy scent that fills the silent loft. Occasionally, he says, a mushroom or two sprouts from the ground.