Banks in this country and airports are some of the worst places to exchange currency. They have poor rates, high commissions, or both.
There are two places exchange houses make money in foreign exchange transactions, the spread between buying and selling rates, and a ''commission'' which is a percentage service charge. In most countries of eastern Europe, I can find exchange houses with a spread between rates of 2% or less and no commission. In some countries it is not difficult to find a spread of 1% or less and no commission. In pre-euro western Europe, in many countries one could find a 2-3% spread and no commission if they looked a little. Now that the euro has arrived, commissions seem to be almost everywhere and the spread has gotten noticably worse, mostly 5% or more. I have seen commissions as high as 10% of the transaction.
ATM's use rates with very low spread because they use the bank-to-bank exchange rates which are the lowest out there. The 1% foreign exchange fee charged by some cards is akin to a commission.
Train stations are also a very poor place to change money, as again they have poor rates and high commission. One exception used to be Keleti station in Budapest the first few times I was there, but that is not true anymore. Many places, one can walk out the door of the station and find exchange houses with good rates and/or no commission, but exchange houses inside the station take you to the cleaners.
There are exceptions to the rule about airports being a poor place to exchange, too. I found decent rates at the Mexico City airport, and the Zurich airport also has decent rates (but it varies by terminal - the exchange house in one termnial charges a commission but the other doesn't and they have the same spread).