There’s a point on the AP-2 motorway in eastern Spain, somewhere between Zaragoza and Barcelona, where you cross the Greenwich meridian line. I’ve driven over it a handful of times and it always catches me by surprise. I guess it’s just not where you expect it to be - the curvature of the earth somehow warps your perception of space and distance in strange ways. A sign unceremoniously announces the imaginary line 500 meters before you cross it and then you drive under a nondescript concrete arc, say “ooh, I didn’t realise that was there” and then get on with your journey and forget about it.