LEWISTON – Sts. Peter and Paul Church, the city’s grandest Roman Catholic church, reopens Sunday after an 18-month renovation.

A new altar will be consecrated as Bishop Joseph Gerry, Auxiliary Bishop Michael Cote, 40 priests and various local leaders attend the first Mass in the upper nave since January 2001.

The church, which was completed in 1938, can hold 1,700 people. “We hope to fill up,” Parish Manager Connie Pleau said.

Pleau said anyone who saw the church before the restoration will be struck by the improvement after work that included the first professional cleaning of the columned space in 64 years.

Soot, dust and rain had stained the walls, turning the white interior a dull gray.

The improvements also include a new $20,000 sound system, a new furnace, new lights and a new baptismal font.

The church’s exterior was repaired two years ago at a cost of $2.3 million, and the most recent work raises the total to $4 million. Church leaders plan to begin developing plans this year for renovations to the upper church.