Praça Pio XII, often called Praça do Cogumelo for its mushroom-shaped water tower, sits on one of Maringá's higher points. It is not a major sight, but it gives a useful view back over the planned city and catches good light near sunset.
Pair it with nearby Grevíleas Park if you want a short walk away from the busier centre. The square also makes a neat local footnote because the Tropic of Capricorn passes through Maringá, one of those small geographic facts the city likes to point out.