Havlíčkovy sady aka Grébovka is one of my favorite parks in Prague. You can go there and have a picnic, read a book, go there to jog or even have a glass of local wine…
Parents with kids will find two playgrounds in the park, one of them is right below the wine cellar (see below). In autumn, it is a great spot to collect fallen colored leaves and chestnuts.
The park was built between 1871-1888 around a villa which belonged to Mr. Moritz Grobe (an important Prague industrialist of his time). You can find many interesting things in Grébovka: the above mentioned villa, an artificial cave (grotto), an ex “gaming house” (and there is a restaurant now).
There is also a wine cellar, which is currently closed until the end of October due to harvest processing.