Currency exchange offices ('Kantor') are easy to find in Warsaw, but as with any international destination, it's imperative to check the rates to ensure you aren't getting fleeced. The general rule is you should never change your money at city entry points, particularly at the airport where the rates are almost criminal. The best place to exchange money, in our experience, is the underpass at Metro Centrum (under the roundabout) where there are a no. of Kantor's competing against each other, therefore, giving you a slightly better rate than you'll get in any of the tourists hotspots. Heading along the main route to the Old Town, you'll see many Kantors, but the rates are not great!