I have a Bernese, not a Newf, but... I live in a walk-up flat in the heart of Toulouse, France. No yard, no dog parks, nothing but a lot of cobblestone streets, but Sam seems to do fine. He gets walked many times throughout the day, from short trips around the block to hour-long strolls. We stayed for Christmas at a house with a yard, and frankly, he wasn't that into it. He doesn't really like to run around a yard and entertain himself. He'd rather nap at home, play with his toys and lean on me while I sit around the apartment. He does love his walks, though! Also, I'll often take him down to our (shared) courtyard at night when it's deserted, and toss around his toys with him. But it doesn't seem to me that a yard is necessary as long as you have the time and desire to find other ways to exercise and entertain your pup!