Anastylosis is an archaeological term for a reconstruction technique whereby a ruined building or monument is restored using the original architectural elements to the greatest degree possible.
This is an integral restoration (a restoration that "puts new pieces in the place of original fragments which have been lost") in which all the elements of a structure are analysed and numbered, following which the building is made structurally sound and rebuilt using original materials as much as possible. Additional materials are used only where structurally necessary.
Anastylosis is also sometimes used to refer to a similar technique for restoring broken pottery and other small objects.
See also Angkor Architectural Styles.