Under the Van Horne viaduct at Clark and de l'Arcade, this was a fenced borough storage yard for years, asphalt and gravel with the look of a dumping ground. Plateau-Mont-Royal put roughly $300,000 into decontaminating the soil, trading pavement for grass and coloured paving, and adding seating and street furniture, then opened the space to the public without ever settling on an official name.

Parc Sans Nom stuck, as did the neighbourhood nickname, Mario Park. It extends parc Lhasa-De Sela eastward along the rail cut, a short walk from the Van Horne skatepark. The grounds are flat and fully accessible, with wheelchair-accessible, gender-neutral toilets on site during programming. Most of the year it works as a plain neighbourhood green space; across a stretch of late-summer weekends it becomes POP Montreal's Marché des Possibles, with free shows, screenings, craft vendors and workshops.