Light makes photography. Embrace light. Admire it. Love it. But above all, know light. Know it for all you are worth, and you will know the key to photography.
~George Eastman
I took this on my smartphone. I have an LG G6. To take a long exposure with a phone or any camera you are going to need a tripod of some kind. I used a blitzwolf selfie stick/tripod. It doesn't matter how steady your hands are, even the smallest vibration will be enough to ruin the photo. My exposure was 3 seconds and ISO 50. I also did a little editing to image with Snapseed.
It is tricky ensuring light levels aren't too high. With a 2-3 second exposure you can sometimes end up with a completely bleached out image if you take it in the daytime, even with the ISO set as low as possible. Your best bet is heading out at sunset or sunrise when it's not completely dark. I got this done early in the morning when the light was not too bright with a longer exposure.