Nonetheless, during the 17th century the new vicar, Joan Arnella, undertook a series of initiatives to revitalise the churches. His restoration efforts focused above all on the building of St. Mary, to mark the commemoration of the 500th anniversary of the act of consecration of the building in 1112.
During the second half of the 12th century, the chapel of Sant Valentí was built. The rear of this chapel now features the only strictly Baroque altarpiece still to be found in Terrassa. It probably dates from the late 17th century, with only the original structure remaining.
Between the 16th and 18th centuries, various altarpieces were commissioned. Three still remain, although none of them is complete: the main altarpiece of St Mary, produced by the artists Baptista Palma and Joan Basí in 1611-12. And the altarpieces of Mare de Déu del Roser, commissioned by the brotherhood of the same name, and painted towards the end of the 16th century. It was located in the transept of St. Mary.
There are records of a further three altarpieces, but only fragments remain. One dedicated to St Sebastian, with three painted panels, was originally located in the church of St. Peter. The main altarpiece of St. Peter, of which three polychromatic sculptures have been preserved; and a third which stood in the church of St. Michael, of which we still have the pediment, two sides and the predella.
The chapel of Santíssim Sagrament was built in the years 1880-1881, annexed to the church of St. Peter and entered via the chapel of Sant Valentí. The current decoration is the result of remodelling work in 1948: the paintings in the presbytery and the vaults of the nave are the work of Ricard Marlet, and the paving mosaics by Santiago Padrós.
The chapel of the Virgin of Montserrat is located in the south transept of Sant Pere. In this chapel stands out the altar presided by a wooden carving of the Virgin of Montserrat. This altar was designed by Josep M. Gassó and sculpted and painted by Francesc Sitjar in 1954.
