This is the spot that marks the traditional exact place of birth of Jesus Christ.
"Fitted into the paving, shines a 14 pointed silver star marking the exact spot surrounded by the Latin inscription: HICDE VIRGINE MARIA JESUS CHRISTUS NATUS EST. 1717. (Here Jesus Christ was born to the Virgin Mary). Of the 15 lamps burning around the recess, six belong to the Greeks, 5 to the Armenians and four to the Latins." [Description from atlastours.net]