Canon EOS 70D Instruction Manual page 60

Q Displaying the Electronic Level
3 Displaying the Electronic Level in the Viewfinder
During Shooting
A simple electronic level using a camera icon can be displayed in the
viewfinder at the center bottom. Since this can be displayed while you
shoot, you can correct any tilt during handheld shooting.
Electronic level
60
1
Select [Viewfinder level].
Under the [z1] tab, select
[Viewfinder level], then press <0>.
2
Select [Show].
Select [Show], then press <0>.
3
Press the shutter button halfway.
The electronic level will appear as
shown in the illustration.
This also works with vertical shooting.
Horizontal
Tilt 1°
Tilt 2° or higher