London moved into the final month of preparations for its Olympic Games on Wednesday with a new landmark to greet visitors, and a warning that some others would not be welcome.

London Mayor Boris Johnson and Seb Coe, chairman of organizers LOCOG, watched as a giant set of interlocking Olympic Rings were eased into place on Tower Bridge across the River Thames.

The rings, 25 meters wide and 11.5 meters tall, are a centerpiece of the "2012 look" that visitors from around the world will experience as they flood into the capital for the Games starting on July 27 and ending on Aug 12.

The Olympic Rings hang from Tower Bridge after being lowered into position for display from the walkways in central London, June 27, 2012. [Photo/Agencies]

"Tower Bridge is recognized the world over and, adorned with the famous Olympic Rings, is the perfect choice to showcase what London has to offer this summer," declared Johnson.

"With just a month to go, we are making our final preparations and want to ensure each and every person in the capital gets a flavor of the celebrations and feels part of the Games."

The Tower Bridge rings, which cost some 260,000 pounds ($405,500) to produce, have been paid for out of a 32 million pound 'Look and Celebration' budget with events scheduled across the capital.

Not everyone will be allowed to attend the party, however. Britain has already refused a visa for the head of Syria's national Olympic Committee, General Mowaffak Joumaa, to travel to London.

Mowaffak is seen as a close friend of Syrian President Bashar al-Assad, who has been strongly criticized by Britain and other Western and Arab nations for a crackdown on an opposition movement seeking his overthrow.

Sports Minister Hugh Robertson told BBC radio that he expected more exclusions in the days and weeks to come.

"Any (applications) that are controversial are referred to the Foreign Office, the Home Office and myself as the Sports Minister and we take decisions on a case by case basis," he said.

"If people apply for visas that have connections with regimes that are guilty of human rights abuses they will not be allowed in... nobody connected with the human rights abuses taking place in Syria at the moment should be part of our Games."

London Mayor Boris Johnson (L) and LOCOG Chairman Sebastian Coe pose for photos on a river boat under Tower Bridge after the the Olympic Rings were lowered into position for display from the walkways in central London June 27, 2012. [Photo/Agencies]

The Olympics may be more of a background hum for many Londoners at present, with the Wimbledon tennis championships dominating current sports headlines, and England's failure to progress beyond the Euro 2012 soccer quarterfinals.

The torch relay is currently in the northeast of England, 40 days in to its journey around Britain before ending up at the new Olympic Stadium in east London for an opening ceremony attended by Queen Elizabeth and other heads of state.