What is Heartbreak Hill at the Boston Marathon?

Heartbreak Hill is the 4th and final climb of the Newton Hills, between miles 20 and 21 (32–34 km) of the Boston Marathon. Its name dates back to 1936: Johnny Kelley catches up to Tarzan Brown there, gives him a friendly tap on the shoulder... and is immediately reeled back in. Brown would win the race, breaking Kelley’s heart. Not steep, but deadly after 32 km.