Curitiba's historical center offers old buildings to admire, nice bars to visit and restaurants where you can enjoy a delicious meal. On Sundays, there's a weekly market which usually gets quite crowded, but it's worth a visit if you wish to buy some local handicraft.
Wikipedia (Portuguese) https://pt.wikipedia.org/wiki/Centro_Hist%C3%B3rico_de_Curitiba
Official website http://www.centrohistoricodecuritiba.com.br/
Address 1155 Alameda Doutor Muricy, Curitiba 80020-040, Brazil
Coordinates -25°25'38.914" N -49°16'27.595" E