How to cover this hole
The previous tenants told us that a radiator used to go there. I don't have a use for this connection so I want to cover it. How do I do it? It's about 4 inches wide (the closeup makes it look bigger). It would be great if the product I use would also serve the purpose of covering wall and floor cracks (all cement). I'm assuming some kind of paste, sand it once dry, and then paint? I'm not in the US so please no brand recommendations since they don't exist here. Thanks in advance, we're moving to this apartment soon, so a lot more questions coming!