The perfect in-city getaway - Yelagin park. Just don't confuse it with the amusement park which is just in front the metro (Krestovsky Island Station). To go to The Yelagin Park you'll need to cross the bridge after you turn right from the subway and walk a little. Because it's the whole island! There is a palace, nice quiet pathways for romantic walks (squirrels and birds included), routes for biking and rollerblading.
In summer it is a popular music festival ground, so you can enjoy the boat rides along the ponds while listening to the music. Picnics welsome as well!
Yelagin Island, St Petersburg, Russia, 197374