بَغْدَادُ مَوْجُودٌ
Baghdad exists.
This illustrates knowing about an object or place that the hearer may never have directly seen. When numerous independent and convergent reports make joint fabrication or error ordinarily untenable, their combined testimony can yield certainty.
Tawātur is not just repeated circulation of the same unsupported story. If a hundred people reproduce one unverified original report, their number does not automatically provide a hundred independent testimonies.
The larger lesson is that direct observation is not the only path to knowledge of external realities. Well-grounded transmission can establish facts beyond our personal experience.