You can, but you'll need to answer the question of why there are no ruins. Civilizations have a strong tendency to build lasting structures that later become ruins: so strong, in fact, that it's basically taken for granted by any culture with any awareness of history as a concept. The tribes might not be particularly historically-aware, but your readers will generally understand that history is a thing. So if there truly are no ruins, you need an answer as to why.
The ruins were destroyed. The civilization left ruins, but some later force -an army, a monster, the gods, alien archaeologists, or whatever- destroyed or otherwise removed them. If you go down this route, you'll need to explain what this force was, and why it wanted to remove the ruins (if the concept of "want" even applies).
The ruins are somewhere else. The events surrounding the fall of this civilization drove people far beyond the civilization's own geographic borders, and something has kept them away ever since. Widespread nuclear fallout is one possibility: to get to the ruins, people would have to venture for so long through highly-radioactive territory that they would die before ever reaching the ruins. Sunken cities are also popular: the ruins are at the bottom of the ocean, and the technology to get there is gone.
That said, it is important that people die before even getting to the ruins. If they were to make it but die on the return trip, they might carry some evidence back a little closer to the tribes. Over several iterations of this, some bits might get far enough that a tribesman could venture in only a little way, find a piece, and survive to bring it back to his people.
People don't know that they're ruins. In this scenario, the tribes live among the ruins, but don't understand them to be ruins. They think it's all a part of the natural order in a basically-untouched wilderness. This is good for civilizations that grew their raw materials, rather than mining or fabricating them, because it allows for the old structures to more easily change their form.
There was nothing to fall into ruin. You could explore the difference between the concepts of "society" and "civilization" by creating an advanced society that did not "civilize" as we tend to think of it: there are no ruined structures because they didn't build structures. This may be the hardest one to pull off, because you have to explain how the society managed to achieve this level of advancement without the advantages that civilization brings. There is another thing to consider: it is hard to imagine that the advantages of civilization would never even occur to an advanced-but-noncivilized society, so you also have to explain why they did not take that path.
There was no society to begin with. An alternative twist on the above would be to dispense with the society completely: they didn't build lasting structures because they didn't exist. But stories of them were written and shared, and these tales became popular as people found meaning in them, and so this metafictional society somehow managed to still have an impact on your fictional world. But this still leaves questions. Who thought of this civilization? How were the first stories written and shared? Why did they leave such a mark on the existing culture that the stories have endured for so long? Do people still understand that this civilization was fictional, or have the stories muddied so much over time that they believe it was real?