You can’t tell from that picture what the walls are like. They are very thick and very tall. Getting out of that prison took help.
Naturally not without outside AND inside help......
This was no small feat by any means. But then all they have to do is spend their time figuring out how to break out.
The two men were in adjoining cells ( so easy planning)
They cut a hole through the back wall, crawling through the opening overnight, scaled a catwalk, then used power tools to drill through metal walls and a steam pipe, finally weaving through interior tunnels... coming out through a manhole cover on the street.