I'm very torn on the monastery in La Rábida as it is after all the place Columbus planned and discussed his journey that would lead to the discovery of the Americas; however, it is padded with modern paintings from the last decade rather than show what it really was like.

Your best bet is to get the audio guide (I think it was included in the price) unless you are with a tour. I've listened to a tour going through and they pretty much got the same info fed as the earphones. It will take you around 45min to get through everything.

As mentioned the new stuff doesn't interest me even if the frescos are nice, but there are original documents on display, dirt from all the American countries (I don't quite get this as they were not established back then) and you get a little bit feeling of the origins of Columbus' journey including miniatures of the ships, again they are not ancient but more there for completing the understanding.