There are fossils in Soria in Spain because about 65-170 million years ago, Spain was covered in tropical seas. Now there is a lot of shelly limestone around and if you're lucky, you can find bits of shells and other sea creature remains.
I have a big collection of some really cool fossils.
Can you see the bits of shells in this limestone?
This one looks exactly like the original shell but it's now stone A neighbour gave it to me.