Arcee had been ordered by Optimus to investigate an abandoned underground human outpost. She stepped through the Groundbridge and it closes and disappeared behind her as she continues.

Luckily, the outpost was huge and so was the elevator used to send in vehicles and large cargo, so she would be able to enter inside and survey it with no issue with her enormity.

She steps onto the large platform and descended down. She reached the bottom after a minute and stepped off before proceeding.