NORTH WOODSTOCK, N.H. — An annual architectural celebration of ice is up and running again in New Hampshire and several other states.

Ice Castles, which are both temporary art installations and tourist attractions, feature towers, tunnels, archways and caves, all created by growing, harvesting and arranging thousands of icicles and then blasting them with sprinklers.

The company behind the displays has expanded since its first installation in 2011. This year it has operations in Utah, Minnesota, two locations in Colorado and New Hampshire, where the site includes a snow tubing hill and ice bar. After a mild winter last year, officials were thrilled that temperatures were cold enough to open earlier this season.

“It’s one of the biggest ice castles we’ve ever built,” said Jared Henningsen, the company’s vice president for operations. “We’re looking at about 25 million pounds of ice spread over two acres.”

As a winter storm brought biting cold and wet snow to the South, visitors to the New Hampshire castle bundled up to explore its twists and turns Friday.

Julia Jones of Gloucester, Massachusetts, said she travels to northern New Hampshire several times a year but had not experienced the ice castles until her opening-day visit.

“I’ve never seen anything like this before,” she said. “Honestly I didn’t think it was gonna be this big.”

Jessica Sullivan, of Fairhaven, Massachusetts, also was surprised, and not just by the frozen environment. Her boyfriend, Brian Jacques, proposed to her during their visit.

“It’s a beautiful place,” said Jacques, who got the “yes” he was hoping for. “I definitely thought, this is the time and place to do it.”

By day the walls and other structures shine with a pale blue hue. After darkness falls, lights embedded within the ice glow pink, purple and green.

“Once you enter into an ice castle, you’re transitioning into something that’s totally immersive and unlike something that most guests have ever seen,” Henningsen said. “I think it inspires people.”