Lifestyle Home Inside Robert Downey Jr. and Wife Susan's Futuristic Malibu Dome House: Our 'Passion Project' The couple spent seven years creating the "unique structure," which serves as their guesthouse By Mackenzie Schmidt Mackenzie Schmidt Mackenzie Schmidt is the Home and Travel Editor for PEOPLE. She's worked at PEOPLE for over five years as a writer and editor on the Lifestyle team. People Editorial Guidelines and Jeff Nelson Jeff Nelson Instagram Twitter Jeff Nelson is the Senior News Editor, Entertainment at PEOPLE. For nearly a decade, he has worked across the brand's entertainment verticals, reporting on breaking news and writing and editing across platforms, as well as securing A-list cover exclusives, including Barry Manilow's coming out and an at-home interview with Madonna. Jeff has appeared as an expert on Good Morning America, Extra, HLN and SiriusXM, as well as at RuPaul's DragCon as a moderator. He studied magazine journalism at Drake University, graduating with a B.A. in Journalism & Mass Communication. People Editorial Guidelines Published on April 8, 2021 08:30 AM Share Tweet Pin Email Robert Downey Jr. and his producer wife Susan are opening their doors to give a tour of their one-of-a-kind Malibu guesthouse. The energy-efficient, dome-shaped house — also known as a "Binishell" after its Italian architect, Nicolo Bini and his father, Dante — is featured in the spring issue of Purist magazine. The eye-catching custom build, which the publication's editor and the Downeys' good friend Cristina Cuomo describes as "caterpillar-shaped" and a "futuristic bubble" sits on seven acres they purchased in 2009 about 500 feet from the couple's more traditional main residence, which they share with son Exton, 9, and daughter Avri, 6. The bulbous structure took nearly a decade to complete. "It was a learning curve in a new arena. Like many 'passion projects' it wound up being a seven-year endeavor," Robert says. The construction uses a process developed in the 1960s. "The outer form is created using large inflatable bladders that are covered in concrete," he explains. Andrew MacPherson for Purist Magazine Andrew MacPherson for Purist Magazine See Inside Grace Harry and Questlove's NYC 'Playroom In the Sky' Apartment Susan described the extended design process, which involved a team of architects, decorators, artisans, and landscapers, as a "balancing trick." More specifically, they had to figure out "how to find items that worked in harmony with this unique structure without falling into parody. Never gilding the lily or having it look like Fred Flintstone's house." Through it all, the Iron Man star adds, "Our contractor never balked at the notion of building within a realm devoid of right angles." Robert Downey Jr for Purist Magazine In addition to being a design feat, the house also offers a seriously reduced carbon footprint. It runs on wind turbines and solar-generated water systems that offset the energy consumption of multiple structures. Robert, 56, and Susan, 47, who are co-founders of the Footprint Coalition, which works to scale sustainable technology, use the space to host friends and family who come to visit. RELATED VIDEO: NCIS's Sean Murray Opens the Door to the Family Home He's Spent 10 Years Designing And it's not just the architecture that makes the Downeys' property remarkable. In addition to hosting human residents, there's also a farm's worth of animals. "Back in 2010 we got two pygmy goats and several horses as gifts," says Robert, "Then I asked Su if we could adopt four alpacas, and she said—yes." Andrew MacPherson for Purist Magazine "I didn't say no. Which he took as yes," Susan clarifies. A decade on, several Kunekune pigs, belted Galloway cows, two Lionhead rabbits and 26 chickens currently call the property home. To read the full feature and see more photos, pick up the print issue — on newsstands Friday, April 9 — or the digital issue, available now.