High achievers: the world's great skyscrapers

London's skyline is rapidly transforming as its latest landmark skyscraper, the Shard, takes the title of Britain's tallest building. Towering above London Bridge train station on the south bank of the Thames, the Shard has already outstripped Canary Wharf's One Canada Square, previously the city's tallest building at 235 metres.

It will eventually rise to 310 metres, making it the tallest building in the European Union when it is completed in May next year.

The pyramid-like, glass structure was designed by Italian architect Renzo Piano. The Shard promises to be a ''vertical city'', with offices, restaurants, a five-star hotel, a spa and some of the swankiest apartments in the capital (shardlondonbridge.com). The 87-storey tower will also feature a public viewing platform on its 72nd floor, which is expected to attract more than a million visitors a year.

Despite these impressive stats, the Shard will not be the biggest in Europe; Moscow's Mercury City Tower, also under construction, will reach 380 metres when it is completed later this year.

And while their sleek design may not be to everyone's taste, no one can deny these megastructures are impressive. Each of them is open to visitors for bird's-eye city views.

Burj Khalifa, UAE

Burj Khalifa opened last year and is the world's tallest building, dominating Dubai's skyline at a jaw-dropping 828 metres high. It has 163 floors of offices, restaurants and a Giorgio Armani-branded hotel. The observation deck is a dizzying 452 metres above the ground. See burjkhalifa.ae.

Taipei 101, Taiwan

The 508-metre Taipei 101 held the title of the world's tallest building when it opened in 2004, until it was dwarfed by the Burj Khalifa. The Taipei 101 still holds the record for the world's fastest elevators, though, taking just 37 stomach-churning seconds to reach the observation deck on the 89th floor.