The memorial to the 2013 Boston Marathon bombing is complete.

Three stone pillars representing the three victims who died at the race's Boylston Street finish line were installed early Monday, marking the final step of the $2 million project, which took four years to plan and develop.

The monument was supposed to be ready last year for the fifth anniversary of the April 15, 2013, bombing but underwent significant redesigns and other delays.

Bolivian-born sculptor Pablo Eduardo said before this year's race that it was important that the final work reflect the hopes and expectations of families who lost loved ones.

The monument marks the spots where two pressure cooker bombs detonated, killing three people and wounding more than 260 others. It includes four bronze and glass spires ranging in height from about 17 feet to 21 feet that were installed last month and are meant to illuminate the site.

Cherry trees to bloom each April have also been planted, and two bronze bricks have been set in the sidewalk to honor the police officers killed in the bombing's aftermath, Massachusetts Institute of Technology Officer Sean Collier and Boston police Officer Dennis Simmonds.

The pillars installed Monday range in height from about 4 to 6 feet and were gathered from places around Boston significant to the bombing victims.

One representing 8-year-old Boston resident Martin Richard was taken from Franklin Park in his family's Dorchester neighborhood. Another that is fused to it honors 23-year-old Boston University graduate student Lingzi Lu and was donated by her school.

Around the base of the two pillars is an inscription etched in bronze: "Let us climb, now, the road to hope."

And the third pillar for 29-year-old Medford native Krystle Campbell comes from Spectacle Island in Boston Harbor. Its inscription reads: "All we have lost is brightly lost."

Boston is also planning a larger monument elsewhere in the city to commemorate the attack.