Excitement bubbled over just inside the entrance, where kids in wheelchairs, parents and medical personnel were eagerly watching the Dark Knight arrive.
In a game room set up for the special visit, a cardboard replica of Batman stood amid piles of Batman-themed crayon boxes, t-shirts, glasses, and necklaces made of bats.
The man behind the costume is Lenny Robinson, 48, a tall, muscular father of three adult children.
For the last 11 years, the wealthy former businessman has dedicated himself to these visits, bringing gifts and a bit of fun to the young hospital patients.
This day, Batman approached 6-year-old Farrah, whose legs were supported by metal braces.
"Farrah, do me a favor," Batman said, leaning towards the shy little girl, before whispering in her ear.
"I never ask kids how they are," Robinson later explained to AFP.
"I say hi, it's nice to meet you, and I give them a present," he said.
Then he tells them to "do Batman a favor: get better. That will make me very happy."
Robinson took up the Batman mantle at the inspiration of his son, who, he said, was "obsessed by Batman."
Robinson inherited the obsession, and then transformed it, ultimately organizing his efforts into a charity: superheroesforkids.org.
He doesn't get paid for his appearances, which average twice a month. Instead he spends some $60,000 (48,159 euros) a year from his own pocket on gifts for the kids. And he spent another $215,000 this year on a new Batmobile, which he donated to the foundation.
Robinson, who sold his commercial cleaning business to great profit in 2007, said he has plenty of time and money for the job.
"I swim, go on vacation, and go be Batman," he smiled. "It's a full time job."
"When the kids know he's coming, there is excitement," said John Herzenberg, head doctor at Sinai hospital's orthopedic wing.
"Anything to divert their attention from their troubles and the pain they are having is a good thing."
Robinson has earned local stardom in his hometown, and his fame only grew last spring when, dressed as the masked vigilante, his Batmobile was pulled over by police.
Officers stopped him because the car -- an earlier version of the Batmobile that was really a decked out Lamborghini -- wasn't displaying its license plates. In their place was the bat symbol.
The police thought they were pulling over "some rich dude in a freaking Batman outfit" who thought he didn't have to follow the rules, Robinson laughed.
Then they realized that Robinson had the real plates in the car -- and that he was on a superhero mission to visit a local hospital.
A video of the incident went viral on the web.
But his mission suffered more of a setback last month, when a gunman massacred 12 people and wounded dozens more in a Colorado movie theater, on opening night of the latest installment of the "Dark Knight" trilogy.
Two hospitals immediately cancelled their long-planned dates with the Winged Avenger.
"The timing was unfortunate for Mr. Robinson's visit, as it was scheduled just three days after the shooting," a spokeswoman for the St. Louis Children's hospital in Missouri, told AFP.
"We felt our patients -- and their families -- needed some time and distance from those images," she explained, adding the hospital planned to reschedule the visit.
"I understand and respect the hospital's decision," said Robinson. "The last thing I want to do is to upset (the children). That would be the opposite of what I want to do."
Despite the shooting, Baltimore's Batman remains in high demand across the US -- with upcoming stops scheduled for Pittsburgh, Pennsylvania and New York. Even European hospitals have requested a visit.
Robinson, who at times adopts the voice of the children's cartoon character SpongeBob SquarePants to avoid scaring the littlest patients, says, unlike the comic book hero, his Batman has no connection to violence.
"I'm the comical, funny, caring, polite, respectful side of Batman," he insisted.