WikiLeaks founder Julian Assange faces a likely extended extradition battle after this week's dramatic end to his seven-year asylum stay holed up in Ecuador's London embassy.

He's now in a British jail, and though UK authorities have yet to confirm the precise place of his detention, multiple reports suggest that he's being held in what's dubbed "Britain’s Guantanamo Bay" — or Belmarsh Prison, given its reputation as a holding facility for terrorists and high profile criminals.

Julian Assange is believed held at the Belmarsh Prison, London

Crucially, the United Nations human rights office has now weighed in, on Friday urging that the UK government holds a fair trial as a US extradition request hangs over the proceedings.

U.N. human rights spokeswoman Ravina Shamdasani told a Geneva news briefing: "We expect all the relevant authorities to ensure Mr. Assange's right to a fair trial is upheld by authorities, including in any extradition proceedings that may take place," according to Reuters.

Meanwhile WikiLeaks editor-in-chief Kristinn Hrafnsson has stated days after Assange being dragged from the embassy on Thursday that he now is confined to a cell at Belmarsh.

The WikiLeaks editor noted that there are some advantages to the location, however, including access to medical care and outdoor time. Hrafnsson also noted it will now be easier for Assange to meet with his legal team, compared to the more restricted environs of the embassy.

"There are medical facilities there, access to dental care I would assume and a garden to go out into," he said.

An RT camera crew has maintained a presence outside Belmarsh Prison since it came to light Assange is being held there, where protests by WikiLeaks supporters are also gaining momentum.

The detention facility is described as follows:

Belmarsh is located on the eastern outskirts of London, about 5 miles (8 km) east of Greenwich on the southern bank of the Thames River. The prison opened in 1991, and has been used to imprison high-profile inmates such as Jordanian cleric Abu Qatada and Salafist preacher Anjem Choudary – but also former Labour MP Denis MacShane, convicted of fraud, and former Conservative politician Baron Jeffrey Archer, convicted of perjury. Belmarsh was also used as the holding facility for around 17 individuals detained under anti-terrorism laws since 2001. Some of them were held in solitary for 22 hours a day, “entombed in concrete” without charges for months, their attorneys told BBC in 2004.

Belmarsh Prison, via The Times

The high-security prison is known to have a capacity of around 900 and contains a mix of inmates on remand serving short sentences alongside those convicted of the most serious offences. But some recent reports say it's been subject to overcrowding in recent years.

The AFP noted on Friday that Belmarsh has housed "some of Britain's most notorious inmates," according to a UK legal source.