Let a point $A$ be joined by a wire to a lower point $B$.
Let the wire be allowed to be bent into whatever shape is required.
Let a bead be released at $A$ to slide down without friction to $B$.
What is the shape of the wire so that it takes same time to descend to $B$ from wherever you release the bead between $A$ and $B$?
The fact that Cycloid has Tautochrone Property was discovered by Christiaan Huygens in $1658$, during his work on developing a reliable and accurate pendulum clock.
The Tautochrone Problem was also solved independently by Niels Henrik Abel in $1823$, using the technique now known as Abel's integral equation.