While superhero movies routinely soar at the box office, none has done so like Chris Nolan’s “The Dark Knight.” Not only did the film please critics and create Oscar buzz for Heath Ledger, “The Dark Knight” trails only “Titanic” for the biggest-ever domestic gross and is just the fourth film to surpass $1 billion worldwide.

Nobody was more surprised by the returns than Nolan, who deliberately went darker than when he resurrected the hero in “Batman Begins.”

“We felt we were really taking risks with a big movie,” Nolan says. “To see people respond in a way you hoped they would, to material that is dark, intense and unconventional, that was the most gratifying and creatively satisfying part. Taking risks and seeing them pay off for a mainstream audience is about as good as it gets for a filmmaker.”

Nolan was unsure how audiences would react after the death of Ledger, and the filmmaker was saddened as he completed a film that introduced the actor’s great gifts to a global stage, knowing it was a farewell performance.

“I felt a tremendous responsibility to deliver to the audience his performance the way Heath wanted it,” Nolan says. “To see people respond to the character that way was a huge relief.”

While Nolan’s vision of the Bat is dark enough to make predecessors seem cartoony, he feels the success is more about the character’s appeal than an audience connecting to material that reflects current dark times.

“I find it hard to talk about these things simply in (terms of) dark and light,” Nolan says. “When you deal with extreme actions by peculiar, colorful, iconic characters, you bring added intensity if you can make people believe what’s going on.

“Escapism is a misunderstood term,” he adds. “If it was as simple as the word is meant to sound, we would all go see musicals about fantastical worlds. To me, escapism is losing yourself in a world that takes you out of your everyday life, but still means something to you. We weren’t trying to make people think as much as feel, using the operatic quality of these iconic characters. Batman is appealing because of his human nature. He’s not a guy with super powers, he’s relatable because he has suffered greatly and tried to channel that into something positive. He is a perfect blend of the elemental qualities and romanticism found in such stories as ‘The Count of Monte Cristo,’ ‘The Prisoner of Zenda’ and ‘Zorro.’ ”

Nolan, who has thrived making films with budgets small (“Memento”), moderate (“The Prestige”) and huge, hasn’t decided yet if he’ll bring back the bat a third time. Burton and Joel Schumacher each stopped at two.

“I loved making a film on a grand scale,” says the director. “It took me back to being a kid and watching movies that were so much larger than life. That’s particularly addictive. But I’ve always been driven by story, first and foremost. It has to fascinate me and make me feel something for a couple of years, because that’s how long it’s going to take to make a film.”