The phrase "several kilometers" means a distance that is more than just a few kilometers, but not a very long distance either. It refers to a measurement that is greater than a couple of kilometers, but less than many kilometers. Full definition
The police had blocked off several kilometers of the highway shoulder and most of the right lane with bright orange construction cones. (bookbrowse.com)
A study by a research team in 2011 came to support this notion, by providing evidence for the existence of lakes several kilometers below the moon's icy surface. (americaspace.com)
To get a better look at the molecular scale we need a «camera» that's several kilometers long, and one such facility is firing up this month. (newatlas.com)