For a short getaway from Rio, the CCR Barcas ferries will take you over to Niteroi which is on the other side of Guanabara Bay. There were different configuration of the ferry based on my two trips and they departed every 20 minutes from either port. The fare was only R5 each way and was a much quicker route to Niteroi versus the traffic jam that I observed on the President Costa e Silva Bridge.
Boarding areas were split into preferred/requiring assistance/60+ years and above and everyone else. However, neither was monitored so it was a little bit of a free for all. After everyone settled in their seats, the ferry wasn't very full at all but this was mid-morning after the rush hour was over.
From Rio to Niteroi, I suggest sitting on the upper deck on the right side which gave you views of Rio. A cafe was located here but wasn't operating. Overall very smooth ride back and forth that took less than 1/2 hour in each direction.
I believe I was the only non-local on each of the ferries so Niteroi wasn't a popular tourist destination. I went to see the UFO shaped Museu de Arte Contempranea but there also was a large shopping mall within 5 minutes walk from the Niteroi ferry building. read more