Any ideas on how to cover a gap in the wall?

[Pannacotta]

There is a tall brick wall between us and our neighbours which I think belongs to them.

For some reason when it was built (before we moved in) a large arch (about 1.5m high and 1m wide) was left in the wall so we can see into his garden and he into ours.

He is not wild about us covering it up but I feel very overlooked, so we need to cover it discreetly, if this is possible.

I did look at arch shape garden/acrylic mirrors but they are all too small.

Is there anything else could we use which woudl look ok from both sides? Or something we coudl lean infront of the gap so it wasnt permanent?

What about cutting a trellis and growing something from a pot up it?

Thanks, sorry I should have said there is trellis covering it now but it still feels quite overlooked from his garden.
I coudl plant a large climber but I woudl really like something which gives more privacy is possible...

a fence
seriously, ivy, fast growing and thick.

Fence would look a bit odd fixed in one section only on top of the wall.
Ivy is an option though.
Any other ideas?

Clematis armandii is evergreen and fairly quick growing - lovely scented flowers in early spring...

'Back board' for basket ball hoop?

Clematis armandii a good idea.
Also like the back board for a hoop thought, but cant do that as its tucked into a corner.
Thanks.