A small circle of dust erupts off the ground as Tewodros drops the enormous gear. “Just in this morning,” he explains energetically. “This is the mesh wheel, from an al Qaeda,” he says, using the local slang for the Isuzu trucks that stampede up and down Ethiopia’s highways, so named for their habit of regularly inflicting vehicular massacre upon any animal, building or car that happens to be in their way, whether on the road or not.

Tewodros points to the other assorted truck pieces scattered in the dirt. “The second speed wheels,” two other hulking pieces of toothed steel, “and also this rear transaxle,” the thick, straight bar covered in black grease stretching between the gears.

Up and down the narrow alley, dozens of identical looking shirtless men, anonymous behind their masks of black grease, are bent down on the ground tinkering over the skeletal remains of hundreds of vehicles that once were. This is the truck graveyard, deep in the heart of the Mercato, and the soundtrack throbbing through the thick, late-summer air is the grunting of men swinging hammers, the cacophony of metal clanging violently against metal and the angry spit of acetylene torches.

Tewodros has never driven a big al Qaeda truck – he’s never driven any motor vehicle – but he can take them apart with a familiarity that most seasoned mechanics would envy. He pulls on his welding mask – a flat piece of cardboard tied around his head with a piece of string and two narrow slits gouged in the front for eye-holes – and begins working the dog-tooth gears onto the axle. Sparks shower around his face, casting weird, midday strobe-silhouette shadows against the building behind him. Five minutes later, a new barbell is lying on the ground. He picks it up, still smoking a bit, and presses it above his head three times, grunting a bit. The veins along his forearms look like they are ready to sprout muscles of their own.

“Good,” he says, “Wufram,” which means fat in Amharic. Tewodros rolls it to me with his foot, and I bend down to try and imitate his technique. I can barely get the weight past my knees before I drop it back onto the greasy dirt. Tewodros laughs and heaves the bar back up to shoulder level. He walks five yards and deposits it on a rusty rack that looks like it’s probably built out of old car door frames. There is enough DIY weightlifting equipment around us to outfit even the most ambitious gym. Squat racks and dumbbells and incline benches and even what looks like a cable machine built using thick iron chains.

Tewodros’s store, his personal gym, is another by-product of Africa’s biggest open-air market. In the Mercato, anything and everything is ready to be taken apart, rebuilt and sold as something else: a hot, dirty, breathing economy of transformation and ingenuity.

“Al Qaeda,” Tewordros shakes his head, laughing. Under the grime covering most of his arm, an enormous bicep is flexing. “Makes you strong.”