Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
Guillermo del Toro directed this movie that was nominated for a best picture Oscar and a few others. It's about carnival sideshows and a grifter (Bradley Cooper) who works his way up to become a successful psychic medium. It's based on the same 1946 novel on which the original Nightmare Alley made in 1947 was based.
At the beginning, we see Stan Carlisle (Bradley Cooper) set fire to his father's house, then hop on a bus that takes him to a carnival. He sees a barker advertising a geek show and he follows the crowd inside. They all gather around a large round wood-lined pit in the ground that is full of straw and snakes crawling on the ground. The barker tells everybody there will be a 25 cent charge to watch him feed the geek, who suckles "on the blood of reptiles and birds." He opens a door down in the pit that exposes the geek sitting on the ground, then he throws a live chicken into the pit. We see snakes crawling on the ground around the chicken. The geek comes into the pit and grabs the chicken then bites its head off. The snakes are there to make the geek's pit look more disgusting and frightening to the audience, but based on the barker's comment, it seems the geek might bite the heads off of snakes as well as chickens.
The snakes are all CGI and because of all of the straw in the pit, they're easy to miss. This is not a snake pit that someone is thrown in as punishment, but it is a pit and it is full of snakes.
Bonus snake stuff: later we see a contortionist advertised as "The World's Most Flexible Snake Man from the Sahara Dunes" rehearsing his act in front of posters that show him as a snake. He twists himself in ways that made my bones hurt just watching him, but It's a stretch to equate him with a snake since snakes don't really contort themselves. But of course, nobody goes to sideshows to learn about natural history.