Step inside the US' new $1 billion embassy in London — the most expensive embassy ever constructed

Slated to open January 16, the new 12-story glass embassy cost $1 billion — the most expensive embassy ever built.

It's been described as a crystalline "sugar cube" and a "modernist museum" that expresses openness and transparency — a far cry from the old fortresslike embassy that embodies a brutalist architectural design, according to the Washington Post.

But make no mistake — the new embassy is highly secure and, as CBS notes, has been described as an "urban fortress."

Take a look inside:

This is the US' new embassy in London. Seated on the banks of the River Thames, it cost $1 billion and will open January 16.

The old US embassy, seen below, opened in 1960 and embodies a brutalist architectural design.

But the new embassy is a 12-story glass cube without visible walls, which the designer, James Timberlake, said he wanted to exude "transparency, openness, equality."

Source: , Washington Post

Timberlake also said he was inspired by European castles — and there's even a moat.

The embassy rests on a hill about 100 feet back from the street, and the moat has waterfalls and deep trenches that could stop a truck bomb. It's even beset by a 6-inch blast wall, which adds to the large price tag.

The building will also produce more energy than it uses: the roof is filled with solar panels, and the white part of the exterior is a plastic polymer that increases it's energy efficiency.

Source: , Washington Post

Here is the lobby entrance, which is adorned with the US State Department embossed seal and the names of every US ambassador to the United Kingdom.

According to the Post, the inside is adorned with "frosted- glass walkways, inspirational quotes from the Constitution, neon sculptures, reclaimed teak benches, Cornwall granite, [and] its own subterranean wastewater treatment plan."

The Evening Standard even called the inside of the embassy "stunning."

Here is a view of the consular lobby, decorated with a sculpture of a typical home in 1950's America.

In the consular section of the embassy is a huge photograph of the Winfield House garden, the official residence of the US ambassador to the UK.

The plastic polymer veil offers a view from the inside out.

There are also a dozen gardens in the embassy.

Above is the Canyonlands Garden, which represents the Grand Canyon and the south west desert landscapes of the US.

This is the visa and consular section.

And here's another angle.

They're still unpacking the consular section.

The embassy also has a bar.

It even has a gym, post office, Marine barracks, and probably a CIA station.

Source: , Washington Post