fisherpon:

The walls from Attack on Titan, recreated in Google Earth and overlaid onto the USA and Europe.

Wall Sina (250km radius): 196,350km²  (75,811mi²)

Senegal, Africa: 196,722km²  (75,955mi²)
Washington, USA: 184,665km²  (71,229mi²)

To fly from one side to the other would take about 0:33.
To take a train from one side to the other would take about 3:56.
To drive from one side to the other would take about 5:00.
To walk from one side to the other would take almost 17 days.

Wall Rose (380km radius): 453,646km² (175,154mi²)

Sweden, Europe: 450,295km²  (173,860mi²)
Caspian Sea, Asia: 394,299km²  (152,239mi²)
Japan, Asia: 377,930km²  (145,920mi²)

To fly from one side to the other would take about 0:50.
To take a train from one side to the other would take about 5:59.
To drive from one side to the other would take about 7:36.
To walk from one side to the other would take about 25 days.

Wall Maria (480km radius): 723,823km² (279,470mi²)

Texas, USA: 695,621km²  (268,580mi²)
Burma, Asia: 676,578km²  (261,228mi²)
Alberta, Canada: 661,848km²  (255,541mi²)

To fly from one side to the other would take about 1:04.
To take a train from one side to the other would take about 7:33.
To drive from one side to the other would take about 9:36.
To walk from one side to the other would take 32 days.