By some very strange coincidence, you're in rio at the same hotel for the same length of time as I was six years ago. Sadly my missus got horrific sunburn so we didn't do much. The only thing I can recommend (and it would be good on your own) would be a day long bus tour including a meal. The one we did cost 200 real and took us up to Christ the redeemer, the maracana, where the carnival goes, the main cathedral and up sugar loaf. May have other bits of it too.
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