Pedra do Sal is a famous samba spot in Rio de Janeiro if you want to experience true and authentic places. It is located in a simple community in the city center, so I recommend coming here with an Uber.
Here, you will find basically a couple of small streets with a lot of bars lined up playing music. There are often live bands playing and people just stand around and dance.
This spot is also known for traditional "baile charme" where everyone in the bar dances to the same choreography. It's honestly super fun to attend!
The samba in Pedra do Sal happens during multiple days of the week, but they are especially known for Monday samba. I recommend checking the schedule before visiting, just in case.