Natural Wonders

Was wondering if anyone had any particular favourite combinations, given the limit of two per city. As far as I can tell they aren't detailed in the manual, so some Civilopaedia data-mining is required. But personally I like to combine the Red Cross with the Pentagon. Units come out with two upgrades as well as medic I. Now that's a useful unit!

Anyone else found some good pairings?

edit: National Wonders, obviously. Nothing Natural about the Pentagon. My mistake!