There is the circular hole in the floor in my living room near radiator which leads to a relatively big space underground! If I want to judge using my eyes,I think the size is around 50cm/1.5feet depth and 30cm/1 foot width and 30cm/1 foot length. I think a mouse entered my house through this hole which is man made. I don't know why there is such a hole near radiator.
I cannot completely fill the hole because it opens to a larger space. I want to lay a plastic sheet over the hole and then push the sheet into the hole. Now I have a cup-like plastic sheet inside the hole which I can fill with cement or mortar.
I am wondering which is better, mortar or cement? I think cement must be better because mortar is made of cement itself and sand and lime. Thus I think the cement must form a stronger piece of solid.
I would be happy to know about other possible solutions too.
Here is a photo: