The world's smallest army, as the Vatican's Swiss Guard is also known, is building new barracks for its elite troops – and for the first time it will include facilities for women.

Swiss Guards have been responsible for the safety of the Pope of the Roman Catholic Church since the 16th century, a record that makes them the oldest military unit in continuous operation in history.

Their iconic costumes – blue berets and doublets, white ruffs, plumed helmets and red, yellow and blue tunics – have a stunning Renaissance flavor.

The traditional rules of recruitment to their ranks are just as old-fashioned: new recruits must be unmarried men with Swiss citizenship, between 19 and 30 years old and at least 1.74 meters tall.

In such a conservative institution, there's no provision for female roles... or there wasn't until now.

The new barracks in the Vatican are being designed to accommodate female Swiss Guards – revolutionary news that comes before the recruitment of women into the Swiss Guard is even officially allowed.

"We planned a new building covering the long-term needs of the Guard," explained Jean-Pierre Roth, chairman of the Swiss foundation funding the construction of the new barracks.

"In many countries, females are integrated in the army or the police. It could also come one day in the Vatican. As careful planners, we had to think about it."

Opening the ranks to women will also help the elite corps to maintain its numbers. Every year, the Swiss Guard recruits 30 to 35 people. There are currently 135 Swiss Guards, most of whom sleep in communal barracks, while the married ones live with their families in separate apartments outside the Vatican.

The new facilities, promise to bring "more space, single rooms, apartments for the families, better quality of the building (humidity, heating) and eco-friendly construction," according to Roth.

Lieutenant Urs Breitenmoser, spokesperson for the Swiss Guard, said: "The primary aim is to build safe and modern new buildings with enough space and privacy for the 135 Swiss Guards, as well as additional apartments for the families who live outside the Vatican walls."

The project, costing $54.49 million, is due to be completed by 2026.

Whether women will be allowed to join the elite corps by then will depend on ratification from the Pope.

A Vatican spokesman traveling with the Pope Francis in Hungary and Slovakia told Reuters that when a papal source was asked about allowing women into the Swiss Guard, they said "We'll see."