Alt-Regensberg Castle was built about the mid-11th century AD by the House of Regensberg in the municipality of Regensdorf. The decline in importance of the castle had been shown already in the Old Zürich War, when Zürich's opponent Alt-Regensberg occupied without resistance. Later the ruins served as a quarry.
The quadratic keep dates from the first construction phase. The exterior of the residential tower has been transformed remarkably over the years. The outer casing of the 11th-century structure was filled with boll stones and mounted in horizontal mortar joints strokes. By 1200 the entire outer surface was chipped away and replaced with carefully edited boss squares. The whole tower thus received a much more upmarket appearance.
In the northern part of the complex is a rectangular foundation wall leaning against the perimeter wall. Here arose in the 12th or early 13th century wooden buildings that served as stables and outbuildings. They were moved to the south and replaced by a palas in the course of the 14th century claimed the whole area between keep and circular wall in the northeastern area.References:
Easter Aquhorthies stone circle, located near Inverurie, is one of the best-preserved examples of a recumbent stone circle, and one of the few that still have their full complement of stones. It consists of a ring of nine stones, eight of which are grey granite and one red jasper. Two more grey granite stones flank a recumbent of red granite flecked with crystals and lines of quartz. The circle is particularly notable for its builders' use of polychromy in the stones, with the reddish ones situated on the SSW side and the grey ones opposite.
The placename Aquhorthies derives from a Scottish Gaelic word meaning 'field of prayer', and may indicate a 'long continuity of sanctity' between the Stone or Bronze Age circle builders and their much later Gaelic successors millennia later. The circle's surroundings were landscaped in the late 19th century, and it sits within a small fenced and walled enclosure. A stone dyke, known as a roundel, was built around the circle some time between 1847 and 1866–7.