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