If you want to feel like a millionaire for a short time, you should go to Vietnam. The Vietnamese Dong (VND) is equipped with many zeros. The currency is only available in Vietnam. Vietnam is a cash society, where much is paid in local currency.
Because the Vietnamese Dong cannot be exported, it is not available abroad.

How to get Vietnamese Dong

Is available in all (medium) large cities. Keep in mind that in smaller towns ATM's emit only small amounts of money (sometimes no more than VND 2 million). Sometimes you can use your card more than once at a time, so you can get more money (you pay costs more than once).

exchanging money
The most commonly used foreign currency is U.S. Dollar (USD). This can be changed in many places. It is a popular currency, as for Vietnamese it is difficult to get USD. Officially they are not allowed to accept it.

VISA and MASTERCARD are accepted more and more. Paying with these cards is not a problem in most hotels and Western restaurants. Usually a pincode is required. 

Obviously the rate subject to fluctuation but an indication of rate:
VND 100.000  ≈  USD 4.48 / GBP 3.48
VND 1.000.000 (1 miljoen) ≈ USD 44.80 / GBP 34.80