Here are just a few places you might find a cross:
• on tattooed arms
• on church signs
• hanging on necklaces
• on the covers of Bibles
• on T-shirts
• in vampire movies
• in your grandma's living room
What'd we miss?
When Mark was writing, the cross hadn't yet become a beloved icon, which people painted, wore, set up in their homes, and branded on their bodies to demonstrate their Christian affiliation or evoke their general respect for religion. No, at that time, the cross was primarily an instrument of execution used by Romans to punish lower-class criminals.
To get down to the nitty-gritty, crosses mean a very slow death, likely by asphyxiation (i.e., lack of oxygen). All the while, the body of the criminal would be on full display, functioning as a big ol' warning to other would-be criminals: this could be you.
Some ancient literary evidence suggests that the cross was particularly potent as a way of punishing lower-class criminals who overstepped their assigned social roles. The logic here is that criminals should suffer punishments that in some way mimic the crime they have committed (Dante loved him some of this). So if they exalt themselves, they will be exalted—literally—but on the cross.
This practice is in keeping with the eye-for-an-eye logic of Jesus's crucifixion: raise this guy high who's a king anyway! Of course, for Mark this is the truth of who Jesus is. So dust off your books from English 101, because in 15:15-39, we're dealing with—yes—irony. We dare you to untangle that one for a term paper.
Up for a challenge? Take a look at the commentary on these verses by Joel Marcus, who tackles these issues head on.
Jesus is killed on a cross—that much is clear. But don't forget, the cross is also what Jesus instructs would-be disciples to carry if they want to follow him (8:34). This could be a figurative way of saying that disciples of Jesus should be prepared for the way of hardship, loss, and perhaps death (regardless of how it comes).
But we can't dismiss a possible literal meaning, either. That is, maybe following Jesus means actually being crucified just like Jesus. Of course, in Mark's world, crucifixion was a real threat for early Christians and we know for a fact that at least some of them living in Rome were crucified by Nero in the year 64 (for more on that, take another look at our "In A Nutshell").
Serious business, right? As much as we love us some tattooed arms, there's more to the cross than meets the bicep.