Top 5 Biggest Construction Projects of All Time

1. NEOM

Estimated Cost: $500–1000+ billion
Status: In progress
Location: Saudi Arabia

NEOM is the largest and most ambitious construction project ever attempted. It spans over 26,000 square kilometers and includes multiple futuristic cities such as The Line, a 170-kilometer-long mirrored megastructure, and Oxagon, a floating industrial complex. NEOM is designed as a carbon-neutral, AI-powered, renewable-energy-driven region — meant to redefine civilization itself.

2. One Belt One Road Initiative (OBOR)

Estimated Investment: Over $1 trillion (across multiple decades)
Status: Ongoing
Location: International (China, Asia, Africa, Europe)

While not a single construction site, OBOR is the largest infrastructure initiative ever launched, covering highways, ports, railways, pipelines, and logistics zones across more than 60 countries. It’s a geopolitical and economic megaproject with massive cumulative costs and global reach.

3. International Space Station (ISS)

Estimated Cost: ~$150 billion
Status: Completed (ongoing maintenance/upgrades)
Location: Low Earth Orbit

A symbol of global cooperation and the most expensive single structure ever built in space. The ISS took over a decade to assemble, involving space agencies from the U.S., Russia, Europe, Japan, and Canada. It remains a functioning science lab and orbiting outpost.

4. King Abdullah Economic City (KAEC)

Estimated Cost: ~$100 billion
Status: In progress
Location: Saudi Arabia

KAEC is a massive planned city on the Red Sea intended to support economic diversification in Saudi Arabia. It includes a port, industrial zones, residential areas, and financial districts. Though overshadowed by NEOM, it remains one of the costliest urban developments in the world.

5. Al Maktoum International Airport (Dubai World Central)

Estimated Cost: ~$82 billion (when complete)
Status: Under construction
Location: Dubai, United Arab Emirates

Set to become the world’s largest airport, it is planned to handle over 200 million passengers annually. The complex will also include logistics zones, commercial and residential districts, and aerospace support infrastructure.