From episode 1x10 "Chidi's Choice". From episode 3x01 "Everything Is Bonzer!".
Marty runs into town and approaches Doc Brown who just sent the other version of Marty back to the future.
Marty rides through Hill Valley in 1985, and later he returns to the square in 1955.
Marty and Doc Brown arrives in Hill Valley in the far future of 2015. Later, Marty walks through the desolate alternate 1985. And finally, he sees Doc Brown setting up the lightning trap in 1955.