most of the buildings that had been constructed around the tower over the years, including the parliamentary legal offices, a stable, a row of houses and the Prime Minister's chauffeur's house, were demolished, and a new garden, College Green, was laid out beside the tower, on top of an underground parking lot. The medieval moat was re-excavated in 1956, and filled with water between 1963 and the 1990s, when its poor water quality led to its being drained and lined with gravel. Several archaeological investigations into the tower were carried out in the post-war period. Investigations were carried out during the renovations throughout 1948 to 1956. Further work followed to the east of the tower between 1962 and 1964, uncovering the landing dock. Another project was carried out in 1994 and 1995, uncovering part of the original garden of the tower and the 16th century adjoining timber house, and an architectural survey between 2009 and 2011 determined that one of the wooden doors on the second floor was probably an original feature from 1365. Tourism In the 21st century the Jewel Tower is managed by English Heritage as a tourist attraction, and protected under UK law as a scheduled monument and a Grade I Listed Building. In 1987 the Jewel Tower and the surrounding site of Westminster Palace were declared a World Heritage Site, the UN noting that the tower formed one of the "precious vestiges of medieval times" in the area. Between 2007 and 2012 an average of 30,000 visitors came to the tower each year, with non-English speaking visitors making up a high proportion. The architecture of the tower has made it a challenging site to operate as a tourist attraction; the fluctuating heat and humidity, and capacity constraints, have prevented it being adapted to house more delicate historical artefacts or accommodate additional visitor numbers. Archaeologists have recovered over 400 objects associated with the tower, and various Delftware drinking jars and an Iron Age sword are displayed inside, along with a set of historiated capitals, described by the historian Jeremy Ashbee as "important and rare examples of English Romanesque sculpture", originating from the Westminster Hall of the 1090s, and a set of weights and measures, on loan from the Science Museum. Architecture The Jewel Tower is a three-storey building of Kentish Ragstone with a brick parapet, structurally largely unchanged since the 14th century. The walls that once faced