The floor plan shows a three-aisled basilica with a transept, choir side towers, side apses and a single western tower.
The coat-of-arms decorated Gothic cross vault was only pulled down in the 16th century after a fire. As part of a renovation in the 1960s, the north aisle was extended to the west around the Lady Chapel, while the south aisle received a new entrance hall. The two north portals, the small “cemetery portal” on the transept and the larger main and lay portal on the side aisle, deserve special architectural attention.
As part of the extensive exterior renovation of St. Peter's, which was completed in December 2004, the former main portal in the west tower was reopened.
Inside St. Peter's, visitors can expect a large number of cult works of art, especially from the Baroque period. Particularly worthy of mention are the figures depicting Christ, Mary and the 12 Apostles, which were made by Wolfgang Stupeler around 1700. The Pietà in the side chapel in the north transept, which dates back to the 17th century, is also worth seeing. Other eye-catchers are the high altar, probably created around 1738 by the Saarlouis sculptor Ferdinand Ganal, with the crowning figure of a pelican, an early Christian symbol, the Gothic plague cross above the altar from the 14th century, the rotary baptism or the statue of St. Nicholas, which was rediscovered and restored just a few years ago. During extensive renovation work in 1984/85, the paintings by the Merzig painter Heinrich Klein, which had been painted over as part of the Second Vatican Council, were uncovered again and who made them in the style of the Nazarene School based on models by Eduard von Steinle.
The parish garden is located outside the church. With an area of 4,000 m², it is part of the “Gardens Without Borders” network. Parish gardens like St. Peter's from the 12th century once secured the pastor's livelihood. At the same time, the garden served as a festival site for the celebration of the patron saint. Framed in an ivy-covered stone wall with a cut flower garden, a classic fruit tree meadow and a flower-filled herbaceous border, a place of contemplation and quiet reflection is created here.
