We went to Forte de Copacabana on one of our first days in Rio.
When you go around Rio, you'll actually notice that almost every point includes some form of fortification with some big ass guns. The Army still runs many of these forts, so there are areas you can visit, and areas that are still considered off limits for civilians.
This particular fort is at the end of Copacabana beach, and most of it is open to the public since it is considered a historical landmark of sorts. The Army still runs this fort, so there are areas you can visit, and areas that are still considered off limits for civilians. Soldiers are "guarding" or watching most of the areas. You can tell it's a pretty easy gig since most of them were trying to stay awake in their folding chair, messing around on their phone, or chatting with fellow soldiers in the area. The fort doesn't have a ton of visitors, and most seemed to be in their late 30's and older, so there wasn't much for soldiers to do outside of answer questions like, "which way do we go to see X?" or, "can we go over there?"
When you enter the fort, there is a guy on the left, who stands completely still like the Queen's Guard in England. The only difference being this guy is by himself, with an old bolt action rifle, and it's only really for show.
Around the entry, there are generally a half dozen soldiers just carrying side arms.
The benefit of these forts being on the points are the amazing views of the surrounding mountains and beaches. They are sitting on some prime real estate.
Here you can see Sugar Loaf in the distance.
At the fort, they have a bunch of old military equipment, everything from cannons through more modern artilery on display. Inside the museum, they have small arms ranging from discovery of Brazil through the late 1800's.
The best thing about the museum is the air conditioning. It was about 95 degrees and the humidity was through the roof the day was there. We hung around the air conditioning units for a while before touring the museum.
The big draw for me was the massive 305mm guns at the fort. The pictures really don't do this gun justice. The cool part about this place is that we could actually go inside and see all of the systems that support this massive gun. Here's the entry:
Due to the low light levels, and the fact I had an iPhone to take pictures, the quality of my pictures are pretty bad of the inside. Here's the hydraulic lift that is used to actually load the gun when it's in use:
We were also able to go on top of the fort to actually see this gun. Here's a picture with a human standing by the business end for scale:
Again, this is a big gun. Here's a shot staring down the barrels:
Inside they do include information on how they load the gun, how they calculate their shots, and they allow you to walk into the rooms that contain their hydraulic systems.
It was a nice way to spend an afternoon and learn a bit about Brazilian history.