Allow at least half a day to visit the Martin Luther King Jr., National Historic Site. The best place to start is the visitor center, where an excellent permanent exhibition traces his life and explains the history of the civil right movement. Other places to visit within this historic site include Ebenezer Baptist Church where he, his father and his brother all preached, and the King Center tomb, where the bodies of MLK Jr and his wife, Coretta, now lie.
If you go:
Book the tour to 501 Auburn Ave. (the house in which King was born) as soon as you arrive, numbers are limited.
Links:

450 Auburn Avenue, NE
Atlanta, Georgia 30312 USA
Phone Numbers:
Park Headquarters
+1 (404) 331-5190
+1 (404) 331-5190
Visitor Information
+1 (404) 331-6922
+1 (404) 331-6922