In Spain you'll find that most ATMs ("cajero automático" in Spanish, "caixer" in Catalan) have a fix withdrawing fee for international cards like Visa/Mastercard. ATMs that have fees are legally obliged to display a screen that indicates the exact amount and ask for confirmation. So feel free to test around, and cancel the transaction if the fee is too high for you.
Your own bank may also add its own fees. This is specific for each bank, so check with your bank pricing to see the fees for international withdrawals.
These ATMs have popped up everywhere in the center of touristic cities in Europe: do not use them. They have horrible fees and push users to withdraw high amounts of cash. Moreover the dynamic exchange rate (if you choose to let the ATM make the conversion for you, never do that) is outrageous.
Don't forget to ask for a receipt, especially when you're abroad. And once you have it, take a picture of it immediately because you'll probably end up losing the paper. Make sure the amount on the receipt matches the amount on your account. And in the case of a dispute, use your receipt/picture as a proof.