dumping ground 
noun
A place where rubbish or unwanted material is left: figurative some estates have become dumping grounds for ‘problem’ families...
- By 1914 Wiltshire's canals had dried up and for many years they became dumping grounds for rubbish as the war pushed any development plans into the background.
- There is a pond between the entrance gate and the main building of the tomb which is completely dry and virtually a dumping ground of rubbish.
- A once-lovely park is now just a dumping ground for rubbish.