Something you will see all over NYC are manhole covers. Some go back to the early 19th Century and taken together they are an iron tapestry illustrating the history of the City.
The earlier examples from the 19th Century and the early 20th Century were made by NYC ironworkers. These men left behind their names on the manholes covers they created and along with a wonderful array of different designs.
Some open into small utility holes and coal chutes but most of them open onto the many tunnels under NYC’s streets that carry all the infrastructure of pipes and electrical wiring that is part of making the city work.
These days most of them are bought from India and China cpountries which can now produce manhole covers more cheaply than anywhere else. If you can see a person’s name on a manhole cover that usually tells you it was made by a NYC worker, usually in the last 2 centuies. Otherwise you will see the names India or China names on them and you will know they are more recent.
The biggest problem with NYC mahole covers is their tendency to explode, see the video. The usual reason is that melted snow and de-icing salt seeps through onto electrical cables causing fraying and eventually fires, smoke and explosions.
Usually people in the vicinity get a fright but sometimes people get hit with a flying mahnole cover which can be a life threatenihng experience. The moral of this story is if you see even a whisper of smoke coming from a mahole cover steer well clear and call the authorities quickly.