Parco del Valentino is a public park situated along the west bank of the Po river in central Turin, opened by the city in 1856 as Italy's first public garden. Its winding roads and formal avenues provided a ready-made layout for a motor racing circuit without the need for dedicated track construction. Between 1935 and 1955 an occasional series of motorsport events — generally known as the Gran Premio del Valentino — was held on the park's roads.
Turin's status as the centre of Italy's automobile industry, home to Fiat and later Lancia and Alfa Romeo's competition activities, made it a natural host for major racing events, and the Valentino circuit operated as a street race in the tradition of the major European city circuits of the interwar period.
The most historically significant event held at Valentino was the 1946 Turin Grand Prix, formally designated the III Gran Premio del Valentino, staged on 1 September 1946. The race drew between 120,000 and 200,000 spectators and was run to the technical regulations of the forthcoming 1947 Grand Prix Formula — allowing either 1500cc supercharged or 4500cc naturally-aspirated engines — making it the first race conducted under what would become Formula One rules.
The field was composed predominantly of pre-war voiturette-class cars, given how recently the Second World War had ended and the absence of the German manufacturers that had dominated pre-war Grand Prix racing. The event was contested primarily between Alfa Romeo and Maserati, with most competitors meeting the 1500cc supercharged specification; the sole exception was Eugène Chaboud, who ran a Delahaye with a 3500cc naturally-aspirated engine.
The 1946 Turin Grand Prix also marked the competition debut of Cisitalia, the Turin-based constructor founded by Piero Dusio. Though neither Cisitalia car qualified for the Grand Prix itself, Dusio won the accompanying Coppa Brezzi race at the same venue the following Tuesday.
The race was won by Jean-Pierre Wimille for Alfa Romeo after a high-attrition event. Rain arrived at the mid-point, by which time half the field had retired. Wimille held the lead into the final laps but was instructed by a pit board to allow team-mate Achille Varzi through to take the victory; Wimille complied on lap 50. Raymond Sommer finished third, two laps down. Tazio Nuvolari retired on lap 10 after losing a rear wheel, which ended up in the Po river.
Valentino Park also hosted the 1948 Italian Grand Prix, one of the premier events in European motor racing at the time. The race brought the Monza permanent circuit's prestigious national Grand Prix to a city circuit setting, underlining the Valentino layout's status as a legitimate Grand Prix venue. The race used the full park-road layout and drew a high-level entry from the leading factory teams.
The 1946 Turin Grand Prix holds a unique place in motorsport history as the generally accepted starting point of the Formula One era. While the official Formula One World Championship did not begin until the 1950 season, the 1946 race was run under the regulations that would define that championship, and is considered by many historians to represent Formula One's true competitive origin.
The park itself continues to function as one of Turin's principal public green spaces. Racing no longer takes place on its roads, but the 1946 event is commemorated as a foundational moment in Italian and international motor racing history.