In the area around Tidan you find lake Östen, which is a typical floodplain lake, nutricious and shallow. It is one of the most valuable bird lakes in the country, and a very important link in the chain of resting places for migratory birds. The beautiful landscape around the lake bears evidence from thousands of years of human activity, and here you can also find several ancient monuments and cultural sights. Lake Östen, together with the rivers Tidan and Ösan, has connected large parts of north and east Skaraborg. A lot of the findings that have been made in the area indicates a very rich district. On your visit here, do not miss the ancient monuments Kung Ranes hög and Askeberga ship cumulus, or the cultural reserve Vallby Sörgården.
The area around Lake Östen bears traces of structures dating back thousands of years. Just south of Odensåker village lies a Bronze Age burial mound which is called Stora Rör. It may contain a chambered tomb where a powerful chieftain rests.
The cairn is c. 29 metres in diameter, 3½ metres high and surrounded by a stone rim or ring consisting of larger stones within. A burial cairn is an ancient grave built like a stone pyramid.
The cairns are not covered with peat, sand or earth but can often have a natural covering of moss. This grave, Stora Rör, has no moss covering however.