Unreinforced concrete has its advantages... this tower still stands after 140 years, and so barring an earthquake it can't withstand it is likely to continue to

Unreinforced concrete has its advantages... this tower still stands after 140 years, and so barring an earthquake it can't withstand it is likely to continue to stand for hundreds more years. Steel-reinforced concrete is considered to have a lifespan of 50-150 years... after that the reinforcement rods will have rusted, and in the process the concrete is likely to have cracked (this is called "concrete cancer"). And since these structures were usually designed in ways that depend on the properties of steel-reinforced concrete, that means they become structurally unsound even if they don't outright fall down. Nowadays for projects meant to last people use stainless steel reinforcement or even carbon fiber reinforcement, but these are expensive.