When travelling to a foreign country, it is advisable to carry a variety of forms of payment. It is important to have cash in US Dollars and local currency, as well as, credit or debit cards. Visa cards are accepted in most places, however, American Express, Discover, and Master Card can be unacceptable in some places. It is advisable is to have several sources of money in case one fails (ATM eats the card, lost cash…).
Spain, Germany, Italy, and the Netherlands all use the Euro form of currency. You may want to buy some Euros before you depart. You can exchange U.S. currency at exchange bureaus in tourist areas, airports, rail stations, major banks, and large hotels. Only paper money can be exchanged, so spend your Euro coins before going home.
The exchange rate of US Dollar vs. other currencies is constantly changing. Please visit XE at http://www.xe.com/ucc/ to get current values.