Marco Zero marks the Equator line in southern Macapá. The monument is simple, but the appeal is obvious: you can stand with one foot in each hemisphere, take the obligatory photo, and look toward the nearby Zerão stadium, whose midfield line is crossed by the Equator.
It is not a long visit, but it is specific to Macapá in a way few city monuments are. Around the equinoxes the site draws extra attention for sun-and-shadow demonstrations.