Here's a question that would stump most trivia quiz contestants: In which countries are the world's five tallest towers?

The surprising answer is: Canada, Russia, China, Iran and Malaysia (in that order).

All five towers are fully described and pictured on the internet. Here's a quick rundown:

Tower No. 1: Toronto, Canada. The 181-storey CN Tower (right), celebrated its 30th birthday on June 29. "Happy thirtieth, CN Tower. Is your run at the top in jeopardy?" asked the Globe&Mail. "Our favourite civic phallic symbol is turning 30," said The Torontoist. "It's still the world's tallest free-standing structure (what does this mean anyway?").

Built by the Canadian National Railway and opened in 1976, the CN Tower is still claimed to be the world's tallest building and free-standing structure. At a height of 553.33m (1,815ft 5in), it attracts two million visitors a year. Apart from enjoying the view, they can walk on a glass floor 342m (1122ft) above ground level, eat at the revolving 360 Restaurant, and see a movie about the tower's construction.

Tower No. 2, Moscow, Russia. Ostankino Tower, also called The Moscow Beauty, is a free-standing TV and radio tower 540m (1772ft) in height. Completed in 1967, it was for 10 years the world's tallest free-standing structure. In August 2000 the tower caught fire, resulting in three deaths and disrupting TV and radio transmissions. It was later restored.

The symbolic nature of the fire at the Ostankino tower recalls the fate of the lighthouse at Alexandria—one of the Seven Wonders of the World. It was built in 279 BC, about 50 years after the widest expansion of Hellenism under Alexander the Great, and reached the fantastic height of 134 meters, till then only exceeded by the Egyptian pyramids. It stood during the darkest periods of the Middle Ages and only collapsed into the sea in 1326, almost 1,600 years later, during an earthquake.
- Patrick Richter.

Tower No. 3: China. Shanghai's Oriental Pearl Tower is the most unorthodox and photogenic of them all. Built between two large river bridges, it's said to create a picture of twin dragons playing with pearls.

The tower is 468m (1536ft) high and can easily be seen as a massive string of pearls. There are three large spheres (the top one is called the space module), five smaller spheres, and three decorative ones at the base. In the topmost "pearl" are shops, restaurants (one of which rotates) and a floor for sightseers. The large lower sphere houses a space city and an interesting sightseeing hall. The Shanghai Municipal History Museum is in the tower's pedestal.

Double-decker lifts (elevators) can whisk as many as 50 visitors up down at seven metres a second.

Tower No. 4, Iran. The Borj-e Milad communications tower in Iran's capital, Tehran, is 435 (1427 ft) high to the tip of its antenna. The main component is a large 12-floor pod near the top. Due to be completed towards the end of 2007, the tower is part of the Tehran International Trade and Convention Centre. It will incorporate a five-star hotel, convention and world trade centres, and an IT (information technology) park.

Tower No. 5, Malaysia. "Amidst the city of Kuala Lumpur stands the Menara Kuala Lumpur at 515m above sea level," says its website. "Majestically poised at a breathtaking height of 421m, the Tower doubles as Kuala Lumpur's best known ambassador."

The concrete telecommunications tower was completed in 1996, and is the tallest tower in south-east Asia. During its construction, builders erected an elaborate retaining wall around a 100-year-old Jelutong tree to avoid having to destroy it.