The phrase "extensive restoration" means a big and thorough process of repairing or renewing something, often involving significant effort and resources to bring it back to its original or desired condition. Full definition
Extensive restoration completed in early 2018 with receipts included. (barrett-jackson.com)
The 8 - meter sculpture, which had been in storage following its last exhibition in Bonn in 1993, recently underwent extensive restoration with the collaboration of the the Calder Foundation and the sponsorship of KPMG France. (museumpublicity.com)
On the occasion of the most extensive restoration of the McKim building's sumptuous interiors in over a hundred years, the Morgan Library & Museum presents an exhibition of photographs by Massimo Listri documenting iconic European libraries that similarly use fine wood, marble, and other precious materials to create an opulent setting for books. (themorgan.org)