These are buildings whose reflective surfaces make them appear to blend into the landscape. They're like the architectural equivalent of the scramble suits from Philip K. Dick's novel A Scanner Darkly.
The Rachel Raymond House, originally designed by Eleanor Raymond, re-visioned by Pedro Joel Costa as an invisible building, Belmont, Massachusetts
(via The Creators Project)
Mirror house, a temporary installation on the Isle of Tyree, Scotland, designed by Ekkehard Altenburger, 1996
The Cira Centre, Philadelphia, Pennsylvania, opened in 2005
Pavilion for an Artist, designed by DHL Architecture, Amsterdam, The Netherlands, 2008
The Mirrorcube, a treehotel in Harads, Sweden, designed by Tham & Videgård, 2008-2010
Pinnacle at Symphony Place, an office and retail skyscraper designed by Pickard Chilton, completed in 2009, Nashville, Tennessee
The first invisible skyscraper ever: the 1,476 ft (450 m) tall Infinity Tower, by GDS Architects, plans unveiled in September 2013.
But how could it disappear from its skyline? ArchDaily explains:
Cameras will be mounted at six strategic points; thousands of LED screens on the facade will then broadcast the real-time photos captured and logged by the cameras.
(via FastCo Design)
Camelot at Cockfosters, a proposed cultural centre designed by a Swedish studio named Råk-Arkitektur, London, UK
Bonus: The partially invisible Lucid Stead, by Philip K. Smith III, within the California High Desert in Joshua Tree, 2013