Broch of Dalsetter, Shetland Isles 
A ruined broch, surviving as a mound of rubble, this broch is noted for its outer defences consisting of two ramparts and a wide ditch between them.
Brochs are circular defended houses with thick (and often hollow) walls which contain galleries, stairways, cells and with a guard cell to the side of the entrance passageway. The best surviving broch is on the Isle of Mousa and it stands to about 13 metres high, but is unlikely to be representative of the height of all brochs. In terms of date, excavated brochs have have fallen within the date range of 600BC-100AD (Iron Age) for their construction, although it has to be remembered that they are often part of complex multi period sites. Brochs are mostly found in the north and west of Scotland.
Here at Dalsetter structures and enclosures relating to a much later farmstead also occupy the broch site - the buildings were depicted as being unroofed on the Ordnance Survey 25 inch to the mile 1st edition (Surveyed: 1878 Published: 1882) map (Shetland Sheet LXV.15).
In the top of the broch mound there is a depression containing a small rectangular single cell structure. A short length of facing stones of the presumed outer face of the broch are visible on the south side of the mound, following a similar curvilinear alignment to these stones is a green depression, presumably a robber trench where the rubble mound has been dug into to remove the facing stones for reuse. The limit of the evidence on the site suggests that the external diameter of the broch was upto about 15 metres.
Grid Reference: HU 40754 15662
This image is of an artificially lit 3d model the site of the Broch of Dalsetter. The 3D Model was produced using Agisoft Photoscan from 171 kite aerial photographs, which produced a model with 102,375,504 faces and 51,194,033 vertices which I reduced to 20,000,000 faces to do the artificial lighting in Meshlab. A little bit of mathematics tells me the camera was at 45 metres.
3D model derived from Kite Aerial Photographs
17 September 2014