I've just returned from Barcelona and used *the long Athens airport walkway* - due to people who have clearly never lived in e.g. London (so don't understand the unwritten rule of keep to the right, I dont use travelators or elevators. I happily sped-walked the journey in about 8 and a bit minutes, arrived at baggage collection with enough time to have a ciggie by which time my case was just coming into view on the conveyor belt. I don't enjoy being forced to sit down for 3 hours (or more) so I find the walk very therapeutic.
The walk at Barcelona airport is much the same distance albeit not underground with interesting murials
Barcelona has frighteningly highly polished marble floors and to me at any rate, makes everything somewhat surreal. They do however provide (free) very easy to push small καροτσάκια (don't know what the right word should be!).
I think the relatively recent revamping at Athens has been a big success - τι κρίμα δεν είναι στην ελληνική κυριότητα but never mind.