Making A Concrete Plant Pot

I've been doing a lot of concreting lately (I'll show you some more of what I've been up to later) so I thought I'd have a mess around with some left over concrete. 

So with some underground pipe, a bit of plywood and half a Vimto bottle (I do love Vimto so much) I knocked up a very simple shutter to pour some concrete into.

Now because all the sides are straight I knew I'd have a bit of difficulty getting it out of the shutter, basically I made it to be cut out afterwards, much quicker for me and as this was only an experiment it didn't matter. 

The pot poured. Shuttering is basically making things in reverse, so here you see the future base of the pot.

And here's the finished pot. I am only messing around and experimenting at his point but I am tempted to make some big planters for my new patio as I find terracotta doesn't last and other big pots are so expensive. I like the modern look of the concrete on the edges, and although I know this isn't to everyone's taste I think it could look quite cool if you had a collection of pots in a group with some striking plants in them. 

I'm planing on making some big square planters on wheels to act as a barrier to the stairs on the patio that can be moved out of the way, as well as some big pots to plant up some acers and other ornamentals in.

What would you make out of concrete? 

(I know I've asked this before on this post here but it's always interesting to here if people have had new ideas)

I also like the look of these.