NEW YORK – Paul Giamatti can’t stop thinking about the Roman Empire.

It’s a lifelong fascination that found its way into “The Holdovers,” for which he earned a best actor Oscar nomination playing a cantankerous ancient history teacher. So when we meet at the Metropolitan Museum of Art on a recent frosty morning, the beloved star is eager to peruse the Greek and Roman galleries. He marvels at a serpentine bronze strigil – a fourth-century skin care tool – and stops to point out a flinty marble bust from the Julio-Claudian period.

“This one is really cool. The guy’s very real-looking!” says Giamatti, winding through a labyrinth of headless statues and terracotta vases. “Growing up, I was always interested in this stuff. Sometimes I wonder if that’s one of the reasons why (my character loves) Rome in the film.”

As we eyeball a set of sea-green armor, a stranger cuts in to share her rave review of “The Holdovers.” “You were amazing. I hope you win the Oscar!” she tells Giamatti, who graciously accepts the compliment. He’s had many of these interactions since the heartfelt dramedy was released in theaters and on Peacock, picking up five Oscar nods including best picture and best supporting actress (Da’Vine Joy Randolph).  

“It’s nice,” he says. “It’s funny, you never know what’s going to strike a chord.”

Paul Giamatti recalls feeling 'guilt' over 'Sideways' Oscar snub

Set at an all-boys boarding school over Christmas 1970, the movie traces the unlikely bond that’s forged between the caustic Paul Hunham (Giamatti), his mutinous pupil (Dominic Sessa) and the school’s head cook (Randolph). It was a familiar world to Giamatti, 56, whose dad was president of Yale University in the late ‘70s and ‘80s. Although, “this guy’s a bit more eccentric than my father was,” Giamatti says.

The project reunites him with director Alexander Payne, two decades after their 2004 hit “Sideways." Giamatti sees parallels between Paul and Miles, his merlot-hating curmudgeon in the wine comedy.

Their smug obsessions “were funny to me,” Giamatti says. “I play a lot of guys who don’t fit in very well. I think over the years, it’s increased my sympathy and empathy for people.” He brings up a moment in “The Holdovers,” when Paul tells a bowling alley Santa that his costume is historically inaccurate.

“I remember thinking it was the weirdest thing, like, ‘What’s the point of this scene?’ ” Giamatti says. But then, he came to understand that “Paul’s pleasure in his own intelligence is also his biggest trap. He doesn’t even realize that he’s being completely awkward.”

"The Holdovers" marks Giamatti's first Oscar nomination for best actor, after a supporting actor nod for the 2005 drama "Cinderella Man." He was surprisingly snubbed for "Sideways," despite nods for his co-stars, but humbly insists that he didn't expect one. “The harder thing to deal with was other people’s disappointment and my own sense of guilt. My agents and managers felt pretty sure something was going to happen, so I felt bad for them.”

Going into Saturday's Screen Actors Guild Awards, he's neck and neck with Cillian Murphy ("Oppenheimer") to win the Oscar, having taken best actor at the Golden Globe, Critics Choice and National Board of Review awards.

“I hope people (in Hollywood) finally realize what a star he is and that he is, in fact, a leading man,” Payne says. “There’s nobody like him; people want to see him. He’s a household name, for Pete’s sake.”

'The Holdovers' star credits 'strange optimism' for his 30-year career

After snaking through Ancient Egypt and the French Renaissance, we eventually wander to a secluded wing of the museum devoted to British artwork. Walking across a creaky wooden floor, we take a seat in the sparsely lit room, where plaster casts of Greek figures Dionysus and Apoxyomenos loom over us.

“In all my years of going to this place, there are still new things I find,” says Giamatti, a native of New Haven, Connecticut, who now resides in Brooklyn with his girlfriend, actress Clara Wong. After graduating from Yale in 1989, he moved to Seattle and cut his teeth as a theater actor, periodically booking roles in TV movies like “She’ll Take Romance.” (“I was Heckler No. 2,” he recalls.)

He eventually broke out in Howard Stern’s 1997 film “Private Parts,” juggling broad family comedies like “Big Fat Liar” with artier fare such as “American Splendor.” “The sense of play is greater for some of them,” Giamatti explains, but he strives to approach everything with the same full-throttle commitment. It’s why he sat in the makeup chair for three hours to shoot a 15-second TV ad in which he reprised his “Planet of the Apes” character, Limbo.

“Why not? It was great!” Giamatti exclaims. “A Japanese Pepsi commercial in ape makeup? That was one of the most interesting things I’ve ever done.”

The Emmy winner has worked steadily for the last three decades, in genres spanning superheroes ("The Amazing Spider-Man 2"), musicals ("Rock of Ages") and historical dramas (HBO's "John Adams"). But he worries at times that he’s “too old” to play certain roles now, including a private detective in a hoped-for project with Payne.  

“It’s brutal,” Giamatti says. “I keep having these horrifying realizations, like, ‘Oh, no, I’m approaching 60, so that would have to be a thing in the movie,’ you know what I mean? That was a shock. There’s stuff that’s gone that I won’t be able to do and things that passed I wish I’d done.”

He’s thought about pursuing things outside of acting, such as drawing or animation. (But frankly, he admits, “I don’t think I know how to do anything else at this point.”) He's grateful for the warm embrace of "Holdovers" from critics and audiences, even as he tries to figure out where exactly he "fits" in Hollywood.

“I still don’t know!” Giamatti says with a laugh. “Sometimes I’m just like, ‘Huh, what a funny career I’ve had.’ Every actor has that: There are tough times where you’re not getting much stuff, and you wonder if it’s still worth doing. But then I would get something I enjoyed, and it’s enough to keep you going until the next one.

“There’s a strange optimism and hope underneath it all.”