Your sentence should start with "My friend and I". I would use the simple past "I was in Rio for ten days".
Student or Learner
I and my friend are speaking about our memories in my house. My friend says "I have been to Rio for ten days".
Is the sentence in present perfect correct? I think the tense is correct but "for ten days" is a little weird to me. Isn't it better to say "I was in Rio for ten days"?
But my problem is if the sentence is correct in present perfect. If it is not correct, can you help me understand why?
I consider 'have been to' incorrect in your sentence because it is used to express the number of times you've visited, but I am not a teacher.
The red part was quoted from http://www.usingenglish.com/forum/th...=1#post1176582