Probably one in Amsterdam/The Netherlands ;)

You can also benchmark your droplet's download speed by downloading this 100mb cachefly test file: http://cachefly.cachefly.net/100mb.test

There's also this script that downloads the file for you, outputs only the speed, and cleans up the temp file:

curl https://kmlnsr.me/speedtest.sh | bash

Source: speedtest.sh