I have a problem that my disk is filling up but I cant find the files that fill it.
When I run `df -h` I get:

 Filesystem Size Used Avail Use% Mounted on
 /dev/root 53G 51G 2.0G 97% /
 devtmpfs 2.0G 4.0K 2.0G 1% /dev
 none 395M 204K 395M 1% /run
 none 5.0M 0 5.0M 0% /run/lock
 none 2.0G 0 2.0G 0% /run/shm
 none 100M 0 100M 0% /run/user

I cleared all caches, logs and auto remove files. When I read this command `du -h /var | sort -nr | head -n 10`
I get:

 1016K /var/www/soFit/cache/class_folder-242/soinfitcom/cl
 1016K /var/www/landing/PHPMailer/vendor
 1008K /var/www/dating/libs/vendor
 988K /var/www/libs/mPDF/ttfontdata
 968K /var/www/landing/PHPMailer/vendor/phpmailer
 964K /var/www/landing/PHPMailer/vendor/phpmailer/phpmailer
 960K /var/www/soFitTest/groupChats/vendor/symfony/http-foundation
 960K /var/www/soFitTest/chat/vendor/symfony/http-foundation
 960K /var/www/soFit/groupChats/vendor/symfony/http-foundation
 960K /var/www/soFit/chat/vendor/symfony/http-foundation

Using `du -xh / | sort -nr | head -n 10`

 1020K /usr/lib/python2.6/lib-tk
 1016K /var/www/landing/PHPMailer/vendor
 1008K /var/www/dating/libs/vendor
 1004K /usr/share/doc/groff-base/examples/hdtbl
 1004K /etc/ssl
 988K /var/www/libs/mPDF/ttfontdata
 988K /usr/share/groff/1.21/font/devlj4
 984K /usr/share/gnuplot
 980K /usr/share/doc/libglib2.0-0
 972K /usr/share/doc/exim4-base


My mysql db size is ~500MB, not that big.

Where is all the 51G of space are gone to?

My linux is:
 Debian GNU/Linux 7.11 (wheezy)