Unfinished building
An unfinished building is a building (or other architectural structure, as a bridge, a road or a tower) where construction work was abandoned or on-hold at some stage or only exists as a design. It may also refer to buildings that are currently being built, particularly those that have been delayed or at which construction work progresses extremely slowly. Many construction or engineering projects have remained unfinished at various stages of development. The work may be finished as a blueprint or whiteprint and never be realised, or be abandoned during construction. One of the best-known perennially  incomplete buildings is Antoni Gaudí's basilica Sagrada Família in Barcelona. It has been under construction since 1882 and planned to be complete by 2026, Gaudí's death centenary. Partially constructed buildings. There are numerous unfinished buildings that remain partially constructed in countries around the world, some of which can be used in their incomplete state but with others remaining as a mere shell. Some projects are intentionally left with an unfinished appearance, particularly the follies of the late 16th to 18th century. Some buildings are in a cycle of near-perpetual construction, with work lasting for decades or even  centuries. Antoni Gaudí's Sagrada Família in Barcelona, Spain, has been under construction for around 120 years, having started in the 1880s. Work was delayed by the Spanish Civil War, during which the original models and parts of the building itself were destroyed. Today, even with portions of the basilica incomplete, it is still the most popular tourist destination in Barcelona with 1.5 million visitors every year. Gaudí spent 40 years of his life overseeing the project and is buried in the crypt. Germany's Cologne Cathedral took even longer to complete; construction started in 1248 and finished in 1880 , a total of 632 years. Buildings (and other architectural structures) never completed. Buildings that were never completed and remain in that state include: Nektarios Shed, London, England In other cases, construction works proceeds extremely slowly, so one can also say form incomplete structures. Examples are: Other unfinished structures. There are also roads, railway lines and channels which remained unfinished. Visions and plans. Many projects do not get to the construction phase, halted during or after planning. Ludwig II of Bavaria commissioned several designs for Castle Falkenstein, with the fourth plan being vastly different from that of the first. The first  two designs were turned down, one because of costs and one because the design displeased Ludwig, and the third designer withdrew from the project. The fourth and final plan was completed and some infrastructure was prepared for the site but Ludwig died before construction work began. The Palace of Whitehall, at the time the largest palace in Europe, was mostly destroyed by a fire in 1698. Sir Christopher Wren, most famous for his role in rebuilding several churches after the Great Fire of London in 1666, sketched a proposed replacement for part of the palace but financial constraints prevented construction . Even without being constructed, many architectural designs and ideas have had a lasting influence. The Russian constructivism movement started in 1914 and was taught in the Bauhaus and other architecture schools, leading to numerous architects integrating it into their style. Use of computer technology. Computer technology has allowed for 3D representations of projects to be shown before they are built. In some cases the construction is never started and the computer model is the nearest that anyone will ever get to seeing the finished piece. For example, in 1999 Kent Larson's exhibition ""Unbuilt Ruins: Digital Interpretations of Eight Projects  by Louis I. Kahn"" showed computer images of designs completed by noted architect Louis Kahn but never built. Computer simulations can also be used to create prototypes of projects and test them before they are actually built; this has allowed the design process to be more successful and efficient.