Which is the tallest building in London that is open for public viewing?

The Shard is the tallest building in London that is open for public viewing, standing at a height of 310 meters (1,016 feet) and featuring an observation deck known as "The View from The Shard." This deck allows visitors to take in panoramic views of the city from one of the highest vantage points in the UK. The building, which opened to the public in 2013, has become an iconic symbol of London's skyline and offers various visitor experiences including guided tours, dining options, and events.

In contrast, while The Gherkin (30 St Mary Axe) and One Canada Square are prominent buildings in London, they do not offer public viewing facilities comparable to The Shard. The Gherkin has an observation deck that was previously accessible to the public but is not currently open for general public viewing. One Canada Square, located in Canary Wharf, is also not open to the public for viewing, as it primarily functions as office space. Each of these buildings contributes to London's architectural diversity, yet none match The Shard's combination of height and public accessibility.