Since Feb 2016 it is possible to legally walk around Skrunda-1 ghost town in exchange for 4 EUR entrance fee. It is a 2h drive from Riga, so I recommend to start early.
We climbed roofs and explored the abandoned buildings for 3h, but managed to see maybe 50%, so you can easily spend the whole day there. Take good shoes and be careful – I ripped my jacket on a nail, and there are broken glasses everywhere. Some photos below: