On a giant construction site, you will find an ice hockey stadium is being bouilt together; there's a skating arena shrouded in scaffolding, and the wasteland in front will soon be a curling centre.

This is the venue for the 2014 Winter Games.Sochi. Although there's a lot to be built, it is not the sporting facilities that is Russia's biggest concern right now - it is security.

At one of the checkpoints, a scanning machine resembling a car wash passes over a lorry delivering building materials. It is searching for traces of explosive.

The head of Russia's Internal Security Service, the FSB, has already warned that terrorists are planning to target the Sochi Olympics.

There is heightened concern following January's suicide bombing at Moscow's Domodedovo airport.

The attacker came from the North Caucasus where Russia is battling an Islamist insurgency. Sochi is right on the doorstep of this volatile region.

"Terrorist attacks in the North Caucasus have an international connection," believes Russia's Deputy Prime Minister Dmitry Kozak.

"Al Qaeda and Arab terrorists are involved. And our secret services have uncovered plans for more attacks. We expect terrorist activity to increase the closer we get to the Sochi Olympics. That's because the terrorists want to attract as much international attention as they possibly can."

At the Olympic CCTV control centre, the guards are on alert. On one of the screens they have spotted an intruder near the perimeter fence. A security team is despatched to the scene but this is no terrorist threat.

The local governor has openly criticised Olympic security

"So far the people we've detained on site have not had any terrorist intentions," says Nikolai Gryznov, Vice President of Olympstroi, the company building and guarding the Olympic facilities.

He believes the security system is well organised as some of the people detained have been found on police wanted lists.