If you start in the middle of the Atlantic Ocean, you’ll hit Portugal, then Spain, then a big chunk of the Mediterranean. It then slides over Turkey, scrapes past Iran, and then Japan gets a nice, thin slice of it.
In the USA, this line is a party. It runs right through Philadelphia, Columbus, Ohio, and Denver, Colorado. Basically, it’s the latitude of pumpkin spice in autumn and sweating through your shirt with iced coffee in July.