Retaining wall around the property

Mainly responsible for the costs would have been foundation work, as well as the concrete walls. The earth for filling would have been the smallest item. I suspect that stone walls could even become more expensive...

Instead of filling in the land, one could limit oneself to the house. Our basement (the white part in the picture with the windows) extends about 3.8m above ground level to the south; below that is a retaining wall that reaches up to 1m above ground level and who knows how far it goes down. Since the house is only 10x10 m wide, it probably didn't cost a fortune. However, the ground is rock and the slope is very steep (over the 10 m length of the house, the ground drops by 3.8 m - the line between brown and white in the south is level with the ground in the north).