Beware of pickpockets as they tend to operate in tourist areas. Keep your belongings secure at all times. Be careful if strangers try to make conversation or distract you as it could be an attempt to steal your valuables.
Bike theft is relatively common in this city, make sure if you are renting or taking your own bike you have a secure lock in place.
Credit card fraud, cloning cards can be an issue be careful where you use your cards. Also if you are withdrawing money from cash machines make sure you cover your pin and be discreet about the amount of cash you withdraw.