BOSTON  — The final pieces of the Boston Marathon bombing memorial have been laid at the site of the 2013 attack.

Three pieces of granite representing the three victims who died at the finish line were placed Monday morning. The installation marks the completion of the $2 million project, which has taken four years to complete after undergoing significant redesigns.

The stones were gathered from places significant to victims Martin Richard, Lingzi Lu, and Krystle Campbell.

The work by sculptor Pablo Eduardo marks the spots where two pressure cooker bombs detonated on April 15, 2013. In addition to the three killed, more than 260 were injured.

The monument also includes four bronze and glass spires that will illuminate the site, cherry trees and bronze markers honoring two police officers killed in the bombing’s aftermath.