But the most impressive part of the project may be the assembly, maintenance, and disassembly of the 75,000 pieces of scaffolding winding around the dome for 2 miles and 25 levels.
This Washington Post's interactive graphic gives a brief overview of the project, and this infographic from the Architect of the Capitol breaks down the phases of the massive repair. The AOC’s “Dome By-the-Numbers” page puts the scale of the project into perspective.