Stones.

I've found in the past that if you use stones for a path etc the weeds always manage to get through. Then you can't hoe them and have to pull them out by hand.

I thought about digging one of my beds soil out to one foot deep and adding stones to bottom then replacing topsoil?

The other daft idea I had was building a stone and cement pillar either side of my entrance gate and setting a planter on top? 

I have always fancied an arch at my gate and I could just build around the arch up to fence level.