When it comes to buying a house or a flat the priority for most of us is price, size and of course location.
In Cornwall the mines may have disappeared but the legacy remains
But how many of us bother to check if there are any hidden hazards lurking underneath such as an old landfill site or even a mine shaft.
Around a third of buyers do not have a survey to find out and it could mean your house is worth a lot less than you thought, or even dangerous.
There are more than 10,000 mines in the UK. Thousands of homes are built above them and some are at potential risk of subsidence.
Belinda Donoghue lives in Redruth in Cornwall. She and her family live next door to a house which was put up for auction with a reserve price of £1,000. It eventually sold for £32,000.
It went cheaply because mine workings had been discovered underneath.
Belinda wants to know if they are under her house too. Real Story is there when she calls in mining consultants to drill under her home to find out.
There are natural faults in the ground which can put your house at risk too.
Eve and Terry Shepherd were woken one night by a strange noise. Huge cracks started opening up in the walls and within hours the front of their house collapsed into a hole. It was caused by a natural fault in the chalk rock under their front door.
There are 33,000 polluted land sites across the country
The Shepherds' home and three others had to be demolished. They have now got planning permission to rebuild their home.
Anne and Brian Parker's home also had to be demolished. But they had forgotten to renew their insurance and have lost everything.
Contaminated land is another problem that can be lurking under your home.
There are 33,000 polluted land sites across the country.
Andrew Pendle's home should be worth £140,000, but estate agents will not touch it.
His home was built on the site of an old gasworks and the garden is so polluted with chemicals children have been warned not to play outside. His home may have to be demolished because the contamination is so severe.
So what should you do if you want to avoid buying a house with a problem underneath it?
Around 70% of house sales now involve an environmental search which looks at possible risks of contamination and other problems. A ground stability survey will highlight any risk of subsidence.
"Forget the granite worktops - the land under your house is what you should be concentrating on. It could affect the value of your home," says property expert Nigel Leck.
Real Story: What is under your home? was broadcast on Wednesday, 28 February, 2007, at 1930 GMT on BBC One.