Hi,

If you say "mile-long", does it refer to "one-mile" something or "a few miles or else"?
For your reference, there are some sentences below.

Thanks~
pb

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The San Luis Valley is known for its high levels of UFO activity. Those who believe in the paranormal say the area is a giant antenna that attracts alien life forms, while Native American legend says it’s a window to other worlds. There have been hundreds of unexplained sightings – everything from mile‐long crafts to fireballs filling the night sky.