Tianluokeng tulou cluster is one of the better known groups of Fujian Tulou. It is located in Fujianprovince, Zhangzhou City, Nanjing County, Shuyang Township, Tian Luo Keng Village (literally "Snail Pit" Village) in southern China. The cluster consists of a squareearth buildingat the center of aquincunx, surrounded by four round earth buildings (or more exactly, 3 round earth buildings and one oval shape earth building).
As told by its owner (Vladimir Agafonkin), SunCalc is an app that shows sun movement and sunlight phases during the given day at the given location, where we can see sun positions at sunrise, specified time and sunset. A thin orange curve is the current sun trajectory, and the yellow area around is the variation of sun trajectories during the year. The closer a point is to the center, the higher is the sun above the horizon.
Here an example: SunCalc at the hardkontt Roman Fort
In a recent paper, entitled "Was Lepenski Vir an ancient Sun or Pleiades observatory?", the authors Vladan Pankovic, Milan Mrdjen and Miodrag Krmar, have discussed the hypotesis of the mesolithic village Lepenski Vir (9500 -- 5500 BC) as an ancient (one of the oldest) Sun observatory. The authors had been so kind to follow a method I suggested of using "freely available software" for the local Sun radiation direction simulation. I used sollumis.com , they used the suncalc.net software.