+1 for everyone in this post.
To use the mv command you do not need to be anywhere in the vicinity of the folder, you just need to know it full path. However if you are above it's folder you can use like the above mention.
Otherwise you can use "mv /path/to/oldfoldername /path/to/newfoldername" . Will also produce the same result. This however you can move rename and also move the folder to a new location if did desired so.