Around 1971 Dave Arneson and his circle of Minneapolis gamers invented games where players controlled individual characters who grew with experience and who could try anything because dice and a referee determined the outcomes. The group tried this style of play in various settings, but Dave invented one that proved irresistible: the dungeon.

Dave’s Blackmoor game—the campaign that spawned Dungeons & Dragons—began with a gaming group playing fictional versions of themselves in a fantasy world. The characters became champions in a series of miniature battles featuring armies clashing above ground. Without dungeons, the Blackmoor game might have stayed miniature wargaming rather than becoming D&D and a game nearly as well known as Monopoly. But by creating the dungeon crawl, Dave invented a new activity that transformed the campaign and ultimately made a lasting addition to popular culture.

The dungeons under Castle Blackmoor began as a minor diversion to the campaign’s fantasy battles above ground, but the Blackmoor bunch spent so much time underground that Arneson ultimately declared the above-ground conflicts lost to forfeit. In a recollection of that first dungeon adventure, player Greg Svenson writes, “By the end of the weekend I had fallen in love with the game.” Dave Megarry of the Blackmoor game wanted to capture the dungeon experience during Arneson’s down time, so he created the Dungeon! board game.

The dungeon crawl contributed as much to the initial popularity of D&D as roleplaying. In the dungeon, D&D brought a fun and evocative activity for a group of players. See (How the Dungeon Powered the Success of D&D and the First Role-Playing Games.

The strangest thing about focusing a game on parties of adventures who explore monster-infested dungeons for treasure is that this activity never happens in the fantasies that inspired the game. At best, you can find elements: traps and treasure in the mummy’s tomb, orcs in Moria, and so on.

The Blackmoor campaign first adapted the Chainmail rules, co-written by D&D co-creator Gary Gygax. But Chainmail never mentions dungeons. At most, the rules suggest using graph paper to map efforts to tunnel under fortifications.

Dave’s Blackmoor games featured a toy castle, which served as the focus for the above-ground battles. Castles can have dungeons, although in 1971 the dungeon of popular fiction was an underground jail rather than a sprawling compound stocked with monsters and treasure.

Nonetheless, in 1972’s second issue of the campaign newsletter, the “Blackmoor Gazette and Rumormonger”, Arneson reported on dungeons below the castle where “heroes went looking for adventure and treasure.” In Playing at the World, Jon Peterson writes, “By this point, Arneson had mapped, on a pad of graph paper, a dungeon six levels deep beneath the castle, with each level containing progressively more formidable adversaries.”

How did Dave Arneson invent the dungeon crawl? By the time people started asking about it, he no longer remembered all the details. Enough clues remain to reveal the specific stories and movies that probably inspired his creation, likely during a June weekend in 1971.

The Hobbit and The Lord of the Rings offer obvious inspiration. J.R.R Tolkien imagines parties of heroes who keep finding themselves in sprawling, underground compounds.

The Hobbit takes readers into the goblin king’s warrens under the Misty Mountains, where Bilbo gets lost in the tunnels and encounters Gollum. Later, Bilbo and his party reach the abandoned dwarven city under the Lonely Mountain, where Smaug sleeps in the “great bottommost cellar or dungeon-hall of the ancient dwarves right at the Mountain’s root.” Even though the tunnels under Lonely Mountain do not fit the definition of a dungeon as an underground jail, Tolkien takes a bit of poetic license and refers to the halls as a dungeon. The Lord of the Rings revisits the dungeon again with Moria, the vast underground compound where the fellowship encounters both orcs and the demonic Balrog.

Dave cites a different inspiration for dungeons. In a 1978 interview that appeared in Wargaming issue 4, he explains. “A local TV station had on several old monster movies, which I watched while eating popcorn and reading old Conan novels. It was then that Blackmoor Dungeon was first conceived.”

His next account of inventing the dungeon crawl comes from his “My Life in Role Playing” article for Different Worlds issue 3, from June/July 1979. “How did it all start in Blackmoor? I can’t really say. I had spent the previous day watching about five monster movies on Creature Feature weekend (ch. 5), reading a Conan book (I cannot recall which one but I always thought they were much the same) and stuffing myself with popcorn, doodling on a piece of graph paper. I was also quite tired of my [Napoleonic] Campaign with all its rigid rules, etc., and was perhaps rebelling against it too (in fact I’m sure I was!!).”

Dave forgot the Conan book and never names the movies that sparked his imagination, but clues lead to some likely answers.

To start, the Horror Incorporated Project compiles a list of all the creature features broadcast on KSTP-TV in Saint Paul – Minneapolis throughout the 1970s.

Blackmoor started with Dave’s toy castle. “I had this neat German plastic kit and I just imagined what sort of fantasy setting it would make,” he recalled in a 2009 interview in Kobold Quarterly issue 9. Meanwhile, on Saturday May 29, 1971, The Black Room (1935) aired on the local station. The movie features a baron’s castle that, like Castle Blackmoor, sits atop a rocky hill and includes a bricked, secret room. But most revealing, the names of the movie and of Dave’s creation just swap two letters. “All this happened a few weeks before the first adventurers caught sight of [the castle].”

So Dave had a castle backdrop for fantasy miniature battles, but perhaps no dungeons yet.

Two weeks later, House of Dracula (1945) aired. This one movie might seem like five because it features all of Universal’s most famous monsters, Dracula, the Wolfman, and Frankenstein’s creation. In a remarkable piece of detective work, Daniel H. Boggs lists several similarities between the House of Dracula castle and Blackmoor. Both stand on rocky pinnacles overlooking a graveyard, a village, and the sea. Both include laboratories and torture chambers. Tunnels underneath both lead to seaside caves.

Castles with underground tunnels, monsters, and torture chambers offer much inspiration, but the Conan book surely provided even more.

While Robert E. Howard never has Conan willingly enter a dungeon, the barbarian often finds himself trapped in dungeons, forced to overcome monsters to earn freedom.

In “Hour of the Dragon,” Conan is imprisoned in the dungeon under the palace of King Tarascus in the Nemedian empire. A sympathetic slave girl gives Conan a rough map of the tunnels, and then warns, “Beyond these dungeons lie the pits which are the doors to Hell.” To escape, Conan defeats a monster that was one of “the goblins of Hyborian legendry, and were in reality ogres of the natural world.”

In “Rogues in the House,” Conan is lost in the pits below the house of the Red Priest, where he evades the traps that slay companions who lack Conan’s “steel-spring quickness.” Although the covered city of “Red Nails” lies above ground, its interior shares the ambiance of a dungeon.

Still, one story presents a dungeon that best resembles those in D&D. In the “Scarlet Citadel,” Conan escapes from “tunnels and dungeons” where an evil sorcerer “performed horrible experiments with beings human, bestial, and, it was whispered, demoniac, tampering blasphemously with the naked basic elements of life itself.” With a torch and sword, Conan explores a maze of tunnels while overcoming monsters.

In 1971, Dave Arneson started with a toy castle, a location inspired by creature features,  and the notion that something might lurk underneath. “[The model] was too small for the scale I wanted,” Dave said. “But it was a neat kit and I didn’t want to abandon it, so the only way to go was down [into the dungeons].”

He added a treasure hunt from Tolkien, traps from Robert E. Howard, lurking monsters from both authors—and perhaps from some creature features—to invent a new activity for the characters in his Blackmoor campaign. When Gary Gygax played one of Dave’s Blackmoor games, the experience so fired Gary’s imagination that he went on to flesh out the game that would become Dungeons & Dragons. In the process, Gary’s imagination and broad knowledge of sword and sorcery would add countless details inseparable from the game. Ultimately, the dungeon crawl proved so compelling that it took root in popular culture.