This job calls for an architect—but a little mountaineering experience wouldn't hurt. Rem Koolhaas and Reinier de Graaf, partners at the Office for Metropolitan Architecture, have conceptualized Rakeen Development's Jebel Al Jais, a mixed-use complex planned for a 6-mile stretch of rugged stone cliffs in the United Arab Emirates. Described by OMA as an "earthly preview of paradise for temporary consumption," the project would feature a convention center, offices, restaurants, and stores in addition to hotels, apartments, and daringly cantilevered villas with roof gardens. Groundbreaking and opening dates are still very much TBA.