Parc de la Ciutadella is located in the southeast part of the city, on the left from Barcelonata subway station. According to wiki, it's supposed to be the second largest park in Barcelona. It is actually situated in the place of the old military citadel which houses the Parliament building, a lake, a waterfall, several museums and a zoo (which we passed).
In the middle of the day we were already too tired for futher walking of any kind, so we decided to take a break in stead.
Ducks swim along with you!