Mads Mikkelsen has described Harrison Ford as a "very nice, monster of a man".

The 56-year-old Danish actor was blown away by how fit the Hollywood legend - who turns 80 in July - did while shooting 'INDIANA JONES 5'.

He told The Hollywood Reporter: "Not just as an actor, but physically. I remember the first day we were shooting, it was a night shoot, then we stopped at 5am — and then he got on his mountain bike and went biking for 50 kilometres.

"Harrison is a monster of a man, a very nice monster.”

Elsewhere, Mads - whose role is not known at this time - said it felt like they were making a Steven Spielberg flick, even though he was replaced by James Mangold.

He explained: "It felt like a Spielberg film, though it’s obviously James making it with the same vision."

Fans can expect a return to Indiana's roots.

The 'Fantastic Beasts: The Secrets of Dumbledore' star added: "It just oozed that golden period of serials from the 1940s — and that’s in the fifth film as well.

“They’re going heavily back to the first and second film and getting that original feel, the original Indy, something dense and epic.”

Last summer, filming was delayed after Harrison suffered a shoulder injury.

Spielberg previously called himself "an idiot" for letting Harrison - who plays the titular character in the iconic action-adventure franchise - do his own stunts, and recalled one in 1981's 'Raiders of the Lost Ark' in particular.

That stunt saw Harrison chased by a huge boulder and Spielberg admitted he was "lucky" to come out of the shoot unscathed.

He said: "There were five shots of the rock from five different angles — each one done separately, each one done twice — so Harrison had to race the rock 10 times.

"He won 10 times — and beat the odds.

"He was lucky — and I was an idiot for letting him try it.”