Here's a nice and easy DIY job anybody can do, whether you want a nice arch seperating your living room and kitchen or something like in these pictures.

First off you need to make your form, whack in a big lump of timber to support the form and start building your form from there, this one isn't really supported enough and the concrete is a bit too thin and not really strong enough, but hell it aint an integeral part of the building so a few cracks down the road later don't really matter, for the curve just use 10mm plywood, to support the curve of the ply just use any old crappy bits of wood you find laying around.

Next you need some rebar, for this 4mm is big enough, 2 lengths going into the wall on either side and tied together using short pieces of rebar every 20cms, doesn't have to be that exact just estimate the distances, chuck the sides on and do your concrete pour.

Because this is such a poncey little beam they are gonna have to leave the supporting form in for about 5 days otherwise it would move or collapse.

At each end you need to fill that area with the little red bricks, render it all off, and then maybe stick some tiles on there to smarten it all up.

Not too bad is it