One of the most important megalithic monuments in Europe is spread over a vast area at Avebury, much of it under Trust protection. The great stone circle, encompassing part of the village of Avebury, is enclosed by a ditch and external bank and approached by an avenue of stones. Many of the stones were re-erected in the 1930s by the archaeologist Alexander Keiller. The site Museum, including an exhibition in the 17th-century thatched threshing barn, presents the archaeological story. Finds from the site and interactive and audio-visual displays are used to tell the story of the monuments and the people who have helped to reveal their past. Nearby, Windmill Hill was once the site of an important Neolithic settlement and has preserved Bronze Age burial mounds. West of Avebury, the Iron Age earthwork of Oldbury Castle crowns Cherhill Down, along with the conspicuous Lansdowne Monument. With the spectacular folds of Calstone Coombes, this area of open downland provides wonderful walking opportunities.