There are lots of amazing buildings constructed with red bricks. Those bricks have been made such a way that they can literally withstand with tons of weights
Especially starforts have been constructed with red bricks in like ine in this picture of Ford Jefferson. These red bricks are denser than modern day bricks and they can be used to build not only rectangular angles but also arched structures too.
An example of a starfort constructed by red bricks.
There are lots of undergroud tunnels all around the world completely made by none other than red bricks.
These red brick tunnels have been part of the old world order ( owo ) and connects all startforts together around the world.
They are water proof and they strong with respect to cement materials of modern world.
Many people still lives in buildings constructed with red bricks in Europe and US.
There must be worldwide brick factory to be able to transfer and construct castles, cathedrals, underground tunnels, starforts and other structures all around the world.
They are also have heat resistance that they can't be melted up to a point but once they melt they become like a glassy object similar to obsidian rocks. And redish color implies there is a oxide form of iron in those bricks. This is also the reason why these bricks are heavier than regular construction materials. Some people call these bricks as Roman bricks but hey, US full of historical buildings constructed by these bricks so they can't be specific to Roman Empire.