The circuit departed Scarperia heading north on the SP503, weaving through several mountain villages to reach Firenzuola. From there it turned west then south on the SR65, passing through Covigliaio, Selva, and Traversa, where the terrain allowed higher speeds. The route then entered the celebrated Futa Pass before descending through Le Maschere and Colle Barucci. Crossing a bridge over a narrow section of Bilancino Lake, the road passed through an ultra-fast left-hander and two long straights before turning onto the SP129 toward San Piero a Sieve, then rejoining the SP503 back to Scarperia. The full lap measured 66.2 km, placing it in the same class of epic distance road races as the Targa Florio and the Mille Miglia.
Motorsport events at Mugello date to at least 1919, with the circuit quickly establishing a reputation for producing skilled and demanding racing. Giuseppe Campari won at Mugello in 1920 and 1921, while Emilio Materassi dominated mid-decade with victories in 1925, 1926, and 1928. Racing activity lapsed for several decades before the Gran Premio del Mugello was revived in 1955, and then again from 1964 to 1970.
The revived format consisted of eight laps of the 66.2 km course, run in a counterclockwise direction through San Piero a Sieve, Scarperia, Violla, Firenzuola, Selva, and San Lucia. The race was incorporated into the World Sportscar Championship for the 1965, 1966, and 1967 seasons. The 1967 edition saw the last World Championship win at the road circuit, taken by Udo Schütz and Gerhard Mitter in a Porsche 910. In 1968, the Alfa Romeo Tipo 33 of Luciano Bianchi, Nanni Galli, and Nino Vaccarella defeated the Porsche of Rico Steinemann and Jo Siffert. Arturo Merzario won the 1969 and 1970 editions in an Abarth 2000, with Abarth claiming a 1-2-3 finish in 1970 as Leo Kinnunen and Gijs van Lennep completed the sweep.
One earlier fatality had occurred on the road circuit: Günther Klass died in an accident during the 1967 race.
The 1970 race proved to be the last on the public road course. During a private test session at Firenzuola, when the roads were open to the public — they were only closed on race day and during qualifying — driver Spartaco Dini crashed his Alfa Romeo GTA into a group of spectators, killing a seven-month-old baby and seriously injuring four others, including two young children. Though the race itself concluded without further incident, the reputational damage was severe and the circuit was permanently retired from use as a racing venue. Dini served two months in prison and subsequently left Italy for many years.
The permanent Mugello circuit was constructed in 1973 and opened in 1974, sited approximately 5 km east of the easternmost section of the original road course. It went on to become one of Italy's premier motorsport venues, hosting the Italian MotoGP annually and, under Ferrari's ownership since 1988, serving as a Formula One testing facility. The permanent circuit hosted its first Formula One race in September 2020, the Tuscan Grand Prix, which was also Ferrari's 1000th Formula One Grand Prix. The legacy of the original road circuit — its mountain passes, extreme length, and connection to the golden age of Italian motorsport — remains part of the Mugello identity.