Correction: An earlier version of this article misspelled the name of one of the firms that designed holes for the mini golf course. It is Grizform Design, not GrazForm Design. This version has been corrected.

Ryan Cohen, 6, left, and Conor Cohen, 7 of Arlington, try to get their balls into any of the three holes in “Piranesi’s Half Pipe.” (Sarah L. Voisin/The Washington Post)

Mini golf is one of the great summertime ­traditions. Head to the closest regional park or ­perhaps a fancy themed course, bring friends and family, and play a round while enjoying the sunshine. Unless it’s 100 degrees . . . in the shade. That’s when you’re ready to melt by the third hole and you wonder why you didn’t choose to go swimming.

The National Building Museum has devised a cool ­solution. It opened an indoor mini-golf course this month that allows players to beat the heat and learn what the museum is about: building, architecture and how both relate to Washington. Twelve local companies were invited to design and build a hole for the course, and the creations are as much fun as the game.

More than a game

The Graf family of Arlington was among the first to arrive on a recent weekday, to start birthday celebrations for Victoria, 10. The four Grafs spent about an hour playing the course, cheering on one another and checking out the designs.

“My favorite hole is Number 5,” said William, 7, who was focused on how the course played, not on what the designers wanted the holes to represent. “Once you get it over the hill, you don’t have to worry.”

“But I could never get it over the hill,” added Victoria. The hole, called “Always a Hole in One,” clearly hadn’t lived up to its name.

Spencer Graf and his daughter, Victoria, wait their turn as Victoria’s brother, William, tries his luck at “Hole in 1s and 0s,” which looks like the inside of a smartphone. (Sarah L. Voisin/The Washington Post)

But Victoria was also interested in the design of the holes. “I liked the one with the neon house the best,” she said of Studios Architecture’s “Canal PARk,” a miniature version of a development near Washington’s Navy Yard that is expected to open this fall. The hole features a box that glows with colored light, a rain garden, mini trees, a carpeted outline of an ice rink and tiny lights substituting for the fountain that is being built at the actual park. It’s fairly easy to get to the hole in two putts. (Ignore the score card, which says that “par” — the number of strokes it should take to reach the hole — is one.)

Harder than it looks

One hole that got attention for its style and playability was “Piranesi’s Half Pipe.” The putting surface of the structure was lined with what looked like an old map. Players stood at the bottom of the half-circle and tried to get their ball into one of three holes. If they missed, the ball eventually rolled back to the starting point. Many kids and adults gave up after three or four tries.

“It looked so easy at first, but I couldn’t get the ball in,” said Patrick McKain, 10, of Gainesville. And Patrick is no mini-golf newbie. He had played a warmup round at another course earlier in the week.

Carmel Greer of District Design said her team knew the hole would be challenging.

“We thought it would be hard, but people say it’s really hard,” Greer said with a laugh. “But every course needs a really challenging hole, right?”

The old map that’s part of the design comes from an 18th-century etching of Rome, Italy, by Giambattista Piranesi, someone well known to architects, Greer said. The idea was to expose other people to Piranesi’s work.

A box and blocks

Although some of the holes have no background information, thankfully Grizform Design’s “Hole in 1s and 0s” does. The huge wooden box with lights and wires along its walls is intended to look like the inside of a smartphone, a device familiar to most Washingtonians.

Victoria and William Graf line up their shots on the “Take Back the Streets” hole. (Sarah L. Voisin/The Washington Post)

Playing this hole involves hitting your ball down a ramp on either side of the box. One ramp is the easier route and guarantees a hole-in-one. Pick the other side and your chance of getting through is about as slim as getting an adult to turn off her smartphone for an hour or two.

That hole’s connection to Washington isn’t obvious, but others need no explanation. “Mulligans on the Mall” has familiar scenes of the city and “Hole Lot of Events” is a doll-size version of a fancy dinner in the Building Museum’s Great Hall.

One hole, “Confluence,” highlights Washington’s two rivers, the Potomac and the Anacostia, but in an unexpected way. Designers at Skidmore, Owings and Merrill took Pierre L’Enfant’s 1791 plan for Washington and matched it with a recent satellite image of the city. They stacked small wooden blocks to show the rivers and what has been built around them. Then they lit the blocks from below to show the water’s paths.

Scott Schlotthauer said that of several ideas the team considered, this design wasn’t supposed to be especially difficult for players.

“It was one of the most complicated to build but one of the easiest to golf on,” he said.

Even so, it’s not smooth sailing. Golf balls often bounce around and get caught on bumps on the river floor. Getting to the hole in two strokes can be tricky.

But luck plays a big part in mini golf. After more than two dozen people walked away discouraged after trying the halfpipe, David Barndollar and his daughter, Mallory, 12, of Reston sank back-to-back holes-in-one.

Asked for advice, Mallory couldn’t offer much.

“I just hit it straight up,” she said with a smile. “That’s all I did.”

Christina Barron