1. Masjid al-Haram, Mecca: $100 billion
Islam's most sacred site and the largest mosque in the world, the Masjid al-Haram in Mecca, Saudi Arabia, which covers 99 acres and can accommodate up to four million people during the Hajj, is estimated to have cost a colossal $100 billion in total.
2. Abraj Al Bait, Mecca: $16 billion
Towering over Mecca, the Abraj Al Bait is a complex of seven skyscrapers that were built in 2012 at a cost of $15 billion to house pilgrims performing the Hajj. The complex is spread out over 34 acres and features the world's largest clock face.
3. Marina Bay Sands, Singapore: $6.2 billion
Singapore's sensational Marina Bay Sands complex wows with the world's most awesome infinity pool, the largest atrium casino ever built, a 2,561-room luxury hotel, and a lot more besides. The landmark complex was completed in 2010 at a cost of over $6 billion.
4. Apple Park, Cupertino: $5 billion
Apple is the richest company in the world with more spare cash than many developing countries, so it's only natural the firm would pump billions into its shiny new HQ in Cupertino, California. The campus, which opened last April, cost an estimated $5 billion in total.
5. The Cosmopolitan, Las Vegas: $4.4 billion
The 3,027-room Cosmopolitan cost an eye-watering $3.9 billion to build in 2009. The art-themed hotel and casino comprises two high-rise towers and houses everything from a 3,200-seat theater to a gargantuan spa and fitness center.
6. One World Trade Center, New York: $4.1 billion
One World Trade Center is the principal building in the rebuilt World Trade complex in New York. Standing a symbolic 1,776 feet (541m) tall, the skyscraper was completed in 2012 at a cost of $3.8 billion, which is $4.1 billion today, and is now the tallest building in the Americas.
7. Palace of the Parliament, Bucharest: $3.9 billion
Thousands of workers died and swathes of Bucharest were destroyed to make way for Romanian dictator Nicolae Ceaușescu's monstrous Palace of the Parliament, which sprawls over tens of acres. The construction of the building, which began in 1984, cost a total of $3.9 billion in today's money.
8. Emirates Palace, Abu Dhabi: $3.8 billion
A hotel rather than a royal residence, the Emirates Palace in Dubai is as regal as they come. Completed in 2005 at a cost of $3 billion, the Kempinski-operated hotel has a total of 394 residences, not to mention two spas, a cavernous ballroom, and scores of shops and restaurants.
9. Wynn Resort, Las Vegas, $3.4 billion
One of the swankiest hotel and casino complexes in Las Vegas, the Wynn resort launched in 2005. The construction bill for this luxury 2,716-room complex hit $2.7 billion, around $3.4 billion in today's money.
10. Istana Nurul Iman Palace, Brunei: $3.3 billion
Built in 1984 at a cost of $1.4 billion, the Sultan of Brunei's eye-opening home is the largest palace in the world that is still in use as a royal residence. The complex contains a total of 1,788 rooms, including a banqueting hall that can seat 5,000 guests.