| 1 | Apollo lunar programme (1961-72) | Aerospace R&D | 2 800 million | (amazon.com) |
| 2 | U.S. Interstate Highway System (1956-92) | Civil infrastructure | 2 400 million | (fhwa.dot.gov) |
| 3 | Channel Tunnel (Eurotunnel) (1987-94) | Mega-tunnelling | 170 million | (reuters.com) |
| 4 | Space Shuttle fleet “turn-round” effort (1981-2011) – ≈1 million h × 135 missions | Aerospace ops | ≈135 million | (historycollection.jsc.nasa.gov) |
| 5 | Hanford Engineer Works (Manhattan Project) (1943-46) | Nuclear/defence | 126 million | (en.wikipedia.org) |
| 6 | Panama Canal – Third-Lane Expansion (2007-16) | Civil-maritime | 110 million | (smithsonianmag.com) |
| 7 | Wikipedia (all languages) (2001-23)† | Collaborative knowledge | 103 million | (stuartgeiger.com) |
| 8 | Portsmouth Gaseous-Diffusion Plant (1952-56) | Nuclear/industrial | 69 million | (energy.gov) |
| 9 | James Webb Space Telescope (1996-2021) | Space science | ≈40 million | (nowhabersham.com) |
| 10 | Golden Gate Bridge (1933-37) | Bridge | 25 million | (history.com) |
| 11 | Three Gorges Dam (1994-2012) | Hydro-power | ≈25 million | (amazon.com) |
| 12 | Hoover Dam (1931-36) | Hydro-power | 22 million | (viewpoint.com) |
| 13 | Burj Khalifa (2004-10) | Supertall building | 22 million | (madmix.co.uk) |
| 14 | Crossrail / Elizabeth Line (core tunnels) (2009-22) | Urban rail | 20 million | (news.ycombinator.com) |
| 15 | Original Panama Canal (1904-14) | Civil-maritime | ≈20 million | (financialservices.house.gov) |
| 16 | Empire State Building (1930-31) | Skyscraper | 7 million | (professionalroofing.net) |
| 17 | Sydney Opera House (1959-73) | Iconic venue | ≈7 million | (youtube.com) |
| 18 | Limehouse Link road tunnel (London) (1989-93) | Urban tunnelling | 5 million | (en.wikipedia.org) |
| 19 | Mont Blanc Road Tunnel (1957-65) | Alpine tunnel | 4.6 million | (en.wikipedia.org) |
| 20 | Gotthard Base Tunnel (1999-2016) | Alpine rail | 4 million | (siemens.com) |
| 21 | Suez Canal “New-Cut” Expansion (2014-15) | Civil-maritime | 4 ½ million | (boskalis.com) |
| 22 | Microsoft Chicago Gen-3 Cloud Datacentre (2008-09) | IT infrastructure | 1.5 million | (slideserve.com) |
| 23 | NASA Space Mountain (Disneyland) (1964-77) | Theme-park eng. | 1 million | (disneydreamer.com) |
| 24 | ISS on-orbit EVA & assembly (to 2025)‡ | Space operations | ≈1 million | (spaceambition.substack.com) |
| 25 | Large Hadron Collider construction (1994-2008) | Particle physics | “tens of millions” | (theatlantic.com) |
| 26 | Event Horizon Telescope (first black-hole image) (2017-19) | Astronomy | 0.6 million | (diffuse.one) |
| 27 | Gotthard Base Tunnel safety systems (Siemens package) | Rail systems | ≈4 million | (siemens.com) |
| 28 | ATLAS LHC end-cap modules (critical path) | Particle physics | 0.05 million | (member.ipmu.jp) |
| 29 | Lego-scale ATLAS outreach model | Ed-outreach | 0.000033 million | (wired.com) |
| 30 | Typical Shuttle orbiter single turnaround | Aerospace ops | 1 million (per flight) | (historycollection.jsc.nasa.gov) |