Exotic plants which had only recently arrived in Britain included Aristolochiaceae, Passiflora and Bignonia. In 1828 the house and estate were purchased by Bishop Augustine Baines to create a seminary and then Bishop William Clifford for a Roman Catholic grammar school which later became Prior Park College. Further landscaping was carried out in the 1880s. In 1993 the park and pleasure grounds were acquired by the National Trust and it was opened to the public in 1996. In November 2002, a large-scale restoration project began on the cascade, serpentine lake and Gothic temple in the wilderness area, this is now complete. Extensive planting also took place in 2007. Future plans include re-roofing the grotto and building a replica Gothic temple. The garden's features include a Palladian architecture bridge (one of only four of this design left in the world), Gothic temple, gravel cabinet, Mrs Allen's Grotto, the ice house, lodge and three pools with curtain walls as well as a serpentine lake. The curtain wall by the lake is known as the "Sham Bridge" and is similar to Kent's Cascade at Chiswick House and Vunus Vale at Rousham House. Ralph Allen was also responsible for the construction of Sham Castle on a hill overlooking Bath. The rusticated stone piers on either side of the main entrance gates are surmounted by entablatures and large ornamental vases, while those at the drive entrance have ornamental carved finials. The Porter's Lodge was built along with the main house to designs by John Wood the Elder. The Palladian bridge, which is a copy of the one at Wilton House, has been designated as a Grade I listed building and scheduled monument. It was repaired in 1936. The Palladian Bridge was later featured on the cover of the 1996 album "Morningrise" by Swedish progressive metal band Opeth. A five-minute walk from the garden leads on to the Bath Skyline, a six-mile (10 km) circular walk around the city that encompasses woodlands, meadows, an Iron Age hill-fort, Roman settlements, 18th-century follies and views over the city.