Is the floor reinforced? Gagosian presents five new sculptures by Michael Heizer, the American land artist, now 77. The monumental works were created in Heizer’s Nevada studio and are part of his “Rock/Steel” series. They see massive rocks (we’re talking many tons) converging with angular steel in a pas de deux of light and shadow, positive and negative space. Think of the gorgeous confrontational balances in George Balanchine’s Agon, but danced by inanimate material of great weight. On a lighter note, five new works on paper round out the show. —Laura Jacobs