A power cut affected around 6,000 Geneva residents, plunging houses in to darkness and trapping people in lifts.
The outage hit Vernier and parts of the city just before midnight on Friday.
The Le Lignon apartment complex was in total darkness for around half an hour. Some climbed more than 20 floors to get home and several more stuck in dark elevators.
Fire teams had to rescue people from four separate lifts during the blackout.
The utility company, the SIG, says a transformer tripped.