By Alastair Leithead

BBC News, Baghdad



The huge dining room's domed roof still stands, as do the pillars decorated with ornate plaster, but everything else in the room is destroyed beyond recognition.

American Rangers used explosives to blow open the entrance

In the middle of the circular hall, where the great and the good of Saddam Hussein's Baath Party would have sat around a huge, luxurious table, are two deep trenches.

Look up, and the two overlapping holes slap bang in the middle of the dome show where the bunker busting bombs entered the palace from more than 12,200 metres (40,000 feet).

Everything else is rubble. Concrete reinforcing rods have been bent around a pillar by the force of the blast.

The walls are deeply charred and daylight streams in through crumbling walls, but underneath the dust, debris and twisted metal is what the American bombs were aiming at.

The whole palace is just an elaborate disguise for Saddam Hussein's nuclear shelter and underground command centre.

It's huge - 1,800 square metres - and was not even scratched by any of the seven bunker buster bombs, or 20 cruise missiles fired at it during the war.

The palace still stands - from the outside just like the many huge lavish buildings that are scattered across Iraq.

But behind the ornate stonework it is like a "wedding cake of thick concrete floors," according to John Carter, a British engineer working in Iraq who has taken a particular interest in the shelter, and even gives tours every now and again to those in the know.

The layers of concrete tricked the specially designed missiles, which 'count' the number of floors they pass through before detonating.

The thick concrete floors tricked the bombs into detonating early

Back at ground level John took me into one of the five entrances to the bunker - the one the American Rangers used, blowing the huge, metal airlock doors to get in.

We went 60 feet down a spiral staircase, along a corridor and up into the shelter which could withstand a nuclear bomb, the size of Hiroshima, going off just 200 metres away.

"You can see how the looters have taken everything," John told me. "I've seen things go steadily over the two years I have been coming here. It's a real shame - if we'd welded up the doors it would have made a great museum."

Engineering feat

And there really is very little left.

First the control room, where the poison gas protection system was monitored, then the TV editing room - a few scraps of tape machines and control panels, but nothing else.

"This is where Baghdad Bob stood and recorded his messages to Al-Jazeera," John said. "The only TV crew allowed in, and they had a war room with a huge raised map on the floor that was all lit up."

Saddam Hussein's suite was the same, with just a small section of his desk remaining in the well-carpeted room. They'd even tried to take the porcelain out of the bathroom - all the taps had gone.

"The man who designed it was the grandson of the woman who designed Hitler's bunker," he added. "It was built by Tito's men in Yugoslavia between 1975 and 1983."

There's a power station, an air filtering plant and water treatment - pipes have been stolen and so water floods into the bunker, but a special system drains into the Tigres so it never floods above floor level.

With dried food, and fresh supplies in the cold storage rooms people could have lived in the bunker for more than 12 months.

The bunker busting bombs hit the palace from more than 40,000 ft

The whole place has a musty, damp smell and no power - in one section, where you can see where the main bunker is separated from the palace on big springs to protect it from a blast - there is a hole in the metal grate floor showing the water beneath.

"We lost a naval commander down there," John laughed, "but we got him out OK - the looters will steal anything that's not screwed down."

And in the biggest of the rooms, again nicely carpeted as it was the Baath Party meeting room, John asked me to look up.

"This is directly under the main dining hall, right where the bombs hit, and it's absolutely fine," he said.

It was. An amazing feat of underground engineering, protected despite the destruction above - it would have made a great museum, and someday maybe it will.