FIVE HUNDRED CHILDREN. On its busiest day, PlayDate PDX, a new indoor mega-rec-room in Northwest Portland, brings in that many tots, their parents and guardians in tow, for hours of amped-up action. It’s not hard to imagine the scene descending into total chaos.

Yet PlayDate, which opened in December, fends off anarchy with a three-story, fairy tale­–themed castle that looms over the 7,500-square-foot space. While it looks like the Middle Ages filtered through a sugar high, the castle is actually an ingenious crowd-control device. Expert hands are at work: British Columbia’s International Play Company, a North American leader in the worldwide play-structure market, custom-built the castle to the specifications of PlayDate’s local owners.

With its intricate threading of slides, ramps, walkways, tubes, battle zones, and dance floors, PlayDate’s palace ranks as one of the most hallucinatory (and entertaining) architectural designs we’ve seen in a long time. Here’s a look at the inner workings of this monumental, inventive citadel of fun.

1. THE GRID International Play design manager Wes Loberg divided PlayDate’s floor into four-by-four-foot squares, allowing him to remix blueprint concepts from International’s 1,000-plus previous structures. Company craftsmen fabricated the stronghold in a 30,000-square-foot workshop outside Vancouver, then took it apart and shipped it to Portland with a team of four.

2. THE SKELETON That modular layout is translated into a three-floor steel framework—which can be snapped apart, reconfigured, or expanded “like Legos,” Loberg says.

3. THE SLIDES The design revolves around slides—Loberg places them first, then arranges other elements around them. International Play is particularly proud of the “helix tube” it developed, reducing the number of plastic components (and labor) needed to make a twisting tubular slide. Loberg also notes that International’s tubes are 36 inches in diameter, rather than industry-standard 30, so grown-ups can ride, too.

4. THE AIR CANNON BATTLE Possibly the coolest element lies outside the castle proper, where two ranks of air cannons blast Nerf-style balls at each other. Loberg’s obvious (but important) insight: “The trick is not to put them so far apart that no one can hit their target, but not so close together that kids are shooting each other point-blank in the face.”

5. THE THEME In a growing and increasingly cutthroat field, International Play prides itself on the richness of its aesthetics. “The business is getting more colorful all the time,” says sales rep Carey Robertson. “But when we say we’re giving you a castle, we give you a castle.” Hand-carved foam turrets and dragon heads highlight a look completed by “bricks” produced on a large-format printer. The only thing missing is the moat.