One of mine is excavating victorian or older landfill or rubbish tips to ,collect the empty glass and pottery containers and bottles. Its very hard to find places to dig in this neck of the woods but theres a lot happening up north. I have two possible sites in sussex but i really need to have geophysical surveys done to know for sure. I went back to one site in kent recently that was under a small field or pasture. It was all under your feet but the developer or someone trashed the site with diggers for reasons unknown probably to stop digging. It may have to be re-excavated as it still may be worth it as there were some goodies under that field. there was 200 years of social history all in a rubbish tip.
If you dont know what i am on about then have a look on ebay. Go to collectables. Then look for Bottles/pots then there are about 15 different categories of bottles. These are what i dig up although the majority on sale are not that interesting. some i wouldnt normally even take home but i did last time as i gave them to the local charity shop as they always sell. The rarities go for a lot of money .