The 100
Sniper Nest
Clarke, Lexa, and Lincoln locate the sniper from Mount Weather who is firing on Tondc in episode 2x13 “Resurrection”.
Massacred Army
Clarke and Lexa are riding back to Arkadia when they come upon the murdered Grounder army in episode 3x05 “Hakeldama”.
Sector 4 Grounder Village
Octavia rides to the Grounder village to warn them of the coming attack in episode 3x06 “Bitter Harvest”.