A lot of the time they build a core filled concrete block wall then construct another stone wall against it. The concrete block wall takes the job of retaining while the stone is for looks only. It does depend on what purpose the wall is performing. For example a retaining wall higher than 600mm (usually) needs engineering by a structural engineer which is easier to achieve with core filled concrete block on footings rather than just solid stone. You never mentioned the purpose of the wall which is a vital detail as there can be numerous ways to achieve similar outcomes.

Actually, @annb1997, think we will go with white mosaic tiles!! The more we thought about it and the more opinions I sought the more it seemed sensible to run the splashback up to the shelf height ie the range hood height. That then became prohibitive for stone, glass or stainless - the tiles are a quarter of the price of taking stone to 300 mm, so 600 mm would have meant crazy $$. Also, we had issues with the thickness of the stone - initially we were told it had to be 20 mm thick, which was impossible with our 14 mm window architraves, but were then advised the stone could be ground back to 12 mm - but then you're paying for something you're not using and paying again to remove it!! Will post a photo with the mosaics in place. What a journey this has been! Moral of the story: quiz your architect about potential issues when asking for a U-shaped corner kitchen ...

I think the look you are going for is gorgeous! But I admit that I too am surprised your considering a smoky mirror splashback if you dislike glass? But again, it all depends on the vision you have for your kitchen. As Dr Retro has wisely pointed out, depending on what is opposite, will depend on what you're reflecting... or, what you have on your kitchen bench and if you want to see it doubled. I think in certain applications, smoky mirror splashbacks can look really beautiful but if you're not fond of glass, why not start with a material that you love and go from there? I have developed a bit of a thing for Southern Cross Ceramics and all the different tiles they have available - in beautiful colour tones, patterns.... aaaaah it's hard to make a decision! It doesn't need to be a dark colour if that is not where you heart lies, but some soft muted colours could work beautifully. I also saw a designer recently laid I believe it was a mix of matt and gloss white subway tiles in a herringbone formation (correct me if I'm wrong anyone??) so that it had a little twinkle here and there... it looked beautiful. As much as I love a mostly white kitchen, I think a little colour & texture that compliments your marble would be a great way to go.I even saw some silver/copper foil looking tiles as part of a splashback to give a kitchen that bit of glam. Before you commit to smoky mirror splashback, maybe have a look at some other options that will compliment your style and see if anything else grabs you :) Good luck.

I wouldn't go those dark laminate kitchen cupboards. I have the exact same and I absolutely loathe them now. I use to love the darker colours but now I wish I had just done them white, light gray or even the dark blue (although dark blue worries me a little too!). That dark laminate brown is such an absolute pain to keep clean. They show up every mark. I like your stone bench tops though but would look at other options to create the look you're hoping for with the joins and waterfall benches etc. Goodluck with it all!