At least one night, we recommend trying the famous Peking Duck, also called lacquered duck, in a first-class restaurant where the prices remain scandalously low. Our favourite is Hua Jia Yi Yuan, on 235 Dongzhimen Street. You'll see lots of tourists and business dinners, but Peking Duck is only available in places like this. For restaurants that cater to everyday Chinese this dish is too much while for restaurants that cater to local nouveau riche it's not enough. In any case, in addition to the duck, the noodles are delicious! Dinner will run you about 100CNY person.
