However, you could use descriptive phrases to convey the idea:
* A heap of rubble
* A pile of rubble
* A mound of rubble
* A mass of rubble
* A jumble of rubble
You could also use more evocative options depending on the context:
* A debris field (if it's from a destruction event)
* A ruin's remains (if it's from a destroyed building)
Ultimately, the best choice depends on the specific situation and the desired effect.