we have the underground railroad slave tunnels still viewable in some homes on the KY side (Covington)
there is/was a "freedom museum" on the Cincy side but I don't know if it folded or not--it was not well established and had some political issues/tickets $$ etc ( I found it--it must still be open)
http://www.freedomcenter.org/
The Museum Center Cincy is in the old Union Terminal whcih has great significance for WWII--as well as natural history and of course there will be CW stuff too.
http://www.cincymuseum.org/

Covington's Basilica Cathedral Madison/11th street is beautiful--their rose window (notre dame duplicate) is outstanding!!

On the western hills of Covington (right off I75) you'll find the
http://www.bcmuseum.org/bcmuseum/default.aspx?pageid=12
Beringer Crawford Museum part of teh CW DIscovery Trail
It's in Devou Park which in itself is lovely!!

There are "steamboats" on the KY side, as well as Newport on The Levee for best views of Cincy
Also--can't miss the Purple People Bridge
http://en.wikipedia.org/wiki/Newport_Southbank_Bridge
Airport is close to city--15-20 mins--parking for city is best on Ky side walk bridge (Roebling is pretty cool--prototype for the Brooklyn Bridge)