An extensive park near the centre of Warsaw is Pole Mokotowskie (Mokotow Fields).  (Use Pole Mokotowskie Metro stop to get there).  It's a great place to walk, jog or hang out.  There a few bars in the park, most famously,Pub Lolek, a place where many a good night has been spent by expat communities and Poles alike.

The park was originally an airfield, where many of Poland's early aviation records were set.  Even giant airships took off from here.  Unfortunately, there is no real evidence left that it was an airfield as the park was reconstructed in the 1970's.

The park can be enjoyed in any season, so here are a few autumnal pics...

One of the best playgrounds in Warsaw is Jordanowski Garden on the corner of Odynca Street and Niepodleglosci Avenue  (known as 'Park Odynca to us), right in the heart of Mokotow.  With a skating hill, football pitch, basketball court, table tennis tables, volleyball net, chess boards, and numerous rides for the younger ones too.  We love it - check it out if you can.