The reason I have visited Belém is because I will travel to the 3 least heard of countries of South America, French Guiana, Suriname and Guyana. From Beléms port, I can take a boat around the Amazon to the city of Macapa on the equator and travel further north by bus to these 3 countries.
I did not do much in Belém, and I did not really find anything I wanted to do there, so it was a good place to relax and enjoy some good Brazilian food, have a walk, and of course buy my boat ticket and find where the port of Belém was.
Overnight boat, Belém to Macapa, 24 hours
I took a Sao Francisco de Paula boat service to Macapa, this was 225 BRL for a private room and significantly cheaper if I would have slept in a hammock outside. The journey time was 24 hours, also the boat was about 6 hours late setting off, so it was a long trip in the end!
Hammocks on the overnight boat service from Belém to Macapa