For me , it's smells. My first job on leaving school was in a shoe repair factory, and whenever I smell leather I am back in the sixties.
My junior school had a distinctive whiff of a sort of urine type smell.It was I think the type of polish used on the floors.Later on I used to teach Brass Instruments, and found some schools still must use the same stuff, as on walking in memory would fly back to my junior school days.
The smell of Gunk on a hot motorbike engine takes me back to my teenage years messing with BSA Bantams, Franny Barnets,James, Ambassadors and others.