The most ubiquitous railway line in the Kansai
region of Japan, called Osaka Kanjô-sen
in Japanese. As the name implies, it runs around Osaka
in a circle: the trains are called uchi-mawari
(inner-looping) when they go counter-clockwise and soto-mawari
(outer-looping) when they go clockwise.
Most trains on the Loop Line are dingy orange-colored locals, called the 101 series, that travel around the loop all day long. (Sometimes you'll hear about a bunch of foreigners getting together and having a party on one of these as it travels around at night, especially on Halloween and New Year's Eve.) Trains from the Hanwa Line and Yamatoji Line also travel around the Osaka loop counterclockwise from Kyobashi to Tennoji (or clockwise from Tennoji to Kyobashi).
Here is my rough ASCII map of the line and connections:
Kobe Line---\ .-------Kyoto Line
| (Umeda) |
Tamagawa Tozai Line---Kyobashi-----Gakkentoshi Line
Nishikujo---Yumesaki Line Osakajo Koen (Osaka Castle Park)
Ashiharabashi Namba Tsuruhashi
| | |
Hanwa Line---' '---Yamatoji Line
Tokyo's equivalent of the Osaka Loop Line is the Yamanote Line