Probably the nicest place to hang out in Nowa Huta if you're having a socialist realism overdose, this reservoir and the surrounding park have served as a recreation ground for the district's hardworking residents since 1957. Unfortunately the area fell into disrepair in the 90s and never fully recovered, rendering swimming off-limits to all those who wish to avoid a nasty E. Coli/fecal bacteria infection. Clearly that's not everyone, as intrepid swimmers can sometimes be seen disregarding the 'no swimming' signs during the warm season. There are plenty of feces-free activities to engage in, however: from kayaking and paddle-boating (rentals available during the summer) to sunbathing and picnicking on the man-made beach to biking on the area's many trails. Fishing is encouraged (the reservoir is regularly re-stocked to appease the local fishermen), and there are also two playgrounds and a sports complex (offering two swimming pools, a basketball court, and a tennis court), plus stands selling coffee and ice cream. Plans are currently underway to modernise the area a bit and add an outdoor stage and pier - all of which should be finished in time for spring 2020. Have fun and don't lose your frisbee in the water.
For further adventure, you can find a trail behind the playground quickly leading to the Jan Matejko Manor House and the next-door 17th-century wooden Church of St. John the Baptist; both sites are seldom open, but make for an interesting glimpse at the village vibes Nowa Huta's colossal concrete corridors wiped out.