Cell Phone

Flip phone?

What frequencies does it support? Unless it supports EU frequencies it won't work.

Is it locked or unlocked? If it's locked you'll pay roaming fees( assuming it works at all) Roaming fees can be so high you're better off buying a cheap unlocked phone in Europe and getting a local SIM for it.

If it's unlocked remove the US SIM and get a Spanish SIM.

All this assumes the phone is GSM. AT&T GSM . Verizon mostly CDMA.