The sun is exactly overhead twice a year in Lahaina, Hawaii, once in May and once in July. Poles don't cast shadows, giving the urban landscape an eerie appearance. Hawaii is the only state in the US where the sun's rays are perpendicular to the surface of Earth. It's called a subsolar point.
Image: Flickr/Daniel Ramirez
Here's Isamu Noguchi's "Skygate" sculpture in Hawaii that makes a perfect ring during the Lahaina Noon:
Here's a real-time map showing the current subsolar sublunar points.