Sentences of a paragraph are given below. While the first and the last sentences (1 and 2) are in the correct order, the sentences in between are jumbled up. Arrange the sentences in the correct order to form a meaningful and coherent paragraph.

1. Stonehenge is a historic site in southern England.
A. It is a religious shrine.
B. At first there was only a circular mound.
C. This was dug in 1900 BC.
D. The familiar circle of giant stones was added 400 years later.
2. These stones weighed about 26 tons each.