The stars in casual outfit visited the site along with a delegation of US Congressmen, according to a leader of the management board of the Hoa Lo Prison Relic.

The actors made the trip on their own programme without contacting the management board in advance, said Dang Van Bieu, deputy head of the management board of the relic.

They toured around the site and talked openly with a group of young people present at the relic, he added.

Pictures of the Hollywood stars quickly attracted attention on the fanpage of the Hoa Lo Prison Relic, and they quickly went viral.

Some fans said they saw the actors at Noi Bai International Airport in Hanoi a few days ago. The actors were wear casual clothes such as T-shirts and shorts.

Located in the center of the capital, Hoa Lo Prison, aka Maison Centrale or Hanoi Hilton, is well-known as one of the most inhumane prisons with terrifying punishment in the past.

Built by French colonists in 1896, the prison was used to house and torture revolutionary Vietnamese leaders. Under the name “Maison Centrale”, Hoa Lo became one of the largest and the most brutal prison complexes in Indochina.

Later, Hoa Lo was used to keep US prisoners of war (POW), who referred to it as the “Hanoi Hilton“. During the 1990s, most of the prison was demolished, but a part has been kept and transformed into a museum, as one of top Hanoi attractions today.