On the eve of Halloween, Marian Goodman Gallery’s sleek London space unveiled its own temporary costume change with a touch of the supernatural, courtesy of the Spanish artist Cristina Iglesias. For her new exhibition Phreatic Zones (until 19 December) she has created an underground river that appears to run beneath the David Adjaye-designed white cube. While the gallery walls are bare, a raised paved floor has taken over the main ground floor gallery. Visitors have to look down for the sculptures—Iglesias has cast tree roots in aluminium and placed them at the bottom of a water course “choreographed” by computer-controlled pumps. The "lost river" emerges from the floor in three places. The artist didn’t have to roam too far for inspiration. “I visited Golden Square Gardens just outside before I started the works and wanted to bring this idea of nature and continuity inside,” she says. The installation in three parts is an "echo", she says, of Tres Aguas in Toledo, the Artangel commissioned works she completed last year that bring the river Tagus into the centre of the historic Spanish city.