I know you're just joking, but concrete is weak in tension and it doesn't bend much before breaking, so they cannot be made like Lego bricks because they will not connect securely.
The closest you can get IMO is the Roman Colosseum. It's mostly made of large blocks with a series of notches in them. Metal bars are placed in the notches so the blocks can move slightly in relation to each other, but not so much as to fall apart.
There's a recycling plant not far from where I take the train. In their yard, they have large (5' x 3') concrete blocks that are "stackable" in that they have voids in their bottoms that fit their counterpart's ridges on the tops—just like a lego.
They stack these 4 or 5 high and create huge U-shaped corrals for various types of metals.
My town does something similar to store rock stalk for the winter—these blocks are stacked and a pre-fab roof is placed directly on top.
To my knowledge, there is no mortar or rebar of any kind, and it can be undone and reworked into another configuration with just a forklift.
These are meant to be temporary, but have been there for >8 and >5 years respectively.
Somewhat related: The famed "Jersey Divider" is cast in a similar way, albeit without any consideration for vertical stacking.
I've heard these called 'Benton Blocks', though, looking that up now, that seems to be a brand [0], not sure if there's a more specific generic term other than 'concrete block'.
> Somewhat related: The famed "Jersey Divider" is cast in a similar way, albeit without any consideration for vertical stacking.
I think Jersey Barriers are usually re-enforced with steel rebar and all the ones that I've seen have a steel cable running through them with a loop at either end to link up to the one next to it, by dropping a pole or similar through both sets of loops, to create a continuous wall. (Though, interestingly, the Wikipedia article [1] doesn't seem to mention that feature.)
