Unknown hole in concrete wall, what could it be?

[mugatu]

A rectangular hole down by the floor in a concrete wall. There has been a timbered wall there once upon a time. Could it be related to that? Or is it something that was there during the casting.
I'm planning to seal it and put tiles on this wall and wonder if it's something to be concerned about?

 

[tergo]

likely holes for form ties that bind the form together during the casting of the wall

 

[jannesspånodamm]

So it is

 

[mugatu]

probably holes for the form ties that bind the form during the wall casting

Ok, good. Then it's just a matter of filling over it, in other words. Thanks!