I remember the tragedy-hit 1994 San Marino Grand Prix at Imola, the one in which the great Ayrton Senna was killed whilst leading the race and the one in which Austrian driver Roland Ratzenberger was killed during qualifying, and a wheel came flying off a car and flew straight into the crowd after a massive start-line pile-up. Many of the spectators were injured.
I was a 12-year-old watching with my dad and it is definitely one of those Grand Prix races that nobody who ever witnessed it will ever forget. It was one of the darkest days in the history of the sport.