"This Structure I Found While Walking In The Woods, The Metal Bit Is About 2 Feet Wide And Looks Like It Could Uncomfortably Fit A Person In It. My Guesses Are A Well, Sewer Or Time Capsule. For Context I Live In Eastern Massachusetts. We Plan On Going Back To Open It"
Answer: "Definitely a man hole. Do not open it. DEFINITELY DO NOT GO IN IT! Manholes are notoriously deadly because they contain low oxygen percentages and high concentrations of poisonous gases such as hydrogen sulfide and methane. First responders usually find two dead people in manholes - the first one that went in and succumbed and their friend who watched them pass out and rushes in to help."
The 25s would be nice