The first barrier is the metal detector.
Everyone attending Copenhagen climate talks has to pass through one every day.
Then there is a second layer of security at the door to the press offices.
Access to the main press conference room is funnelled to a single lane by huge temporary white walls.
Every person's badge - already scanned at the entrance to the conference venue - is re-checked at the end of the funnel.
All this was before Barack Obama and the other world leaders arrived.
From today, when the leaders sit down in a make-or-break attempt to reach a climate pact, there will be no getting near the negotiating rooms.
Journalists can at least be grateful that they are inside the walls.
Overcrowding and security worries have resulted in a cull of pass numbers for non-government observers from the roughly 20,000 who were allowed to register initially to about 7000 on Wednesday and 1000 yesterday.
Many who registered never set foot in the conference centre, even after hours of waiting in the bitter cold.
A second official venue has been organised so official pass-holders can watch proceedings on television.
Frustration boiled over into noisy protests on Wednesday, when disgruntled would-be watchers tried to force their way into the conference and others walked out in solidarity.
The dwindling numbers of observers coincided with an increase in the size of the media contingent, so when the fed-up watchers marched out, they were almost outnumbered by cameramen.
Outside, journalists saw two protesters being hit with batons, while elsewhere police fired teargas.
This was minor in comparison to the main protests in Copenhagen, but the events added to the darker atmosphere.
Asked how he felt about the actions of the Danish police, UN climate head Yvo de Boer said protests inside the centre "tested his courage" to continue with plans to bring 100 world leaders inside.
After days of snail-like progress and disagreements, de Boer's hopeful metaphor for the talks came back to haunt him.
Asked how his "smooth cable car to the summit" was getting on, he responded that it had come to an unexpected stop but he expected it to get moving again soon.