Before its flooding, the canyon of the Daugava River between Pļaviņas and Koknese was one of the most outstanding and beautiful parts of the Baltic terrain, and Oliņkalns hill was one of the largest castle hills in Latvia.  The Andrejs cliff as up to 20 metres high, and it was part of the Daugava canyon.  Before the area was flooded because of the construction of the Pļaviņas hydroelectric power plant, there were rapids near the hill that made it hard for rafters to sail down the river.  Today it is a small island in the reservoir of the plant (it can be seen from the side of the Rīga-Daugavpils highway (A6) opposite Stukmaņi).  It is separated from the shore by 300 metres of river, under which the Dūņas valley is now resting.  A small part of the ramparts of the castle hill can still be seen on the island along with the ruins of an open-air stage and a few metres of the dolomite cliff that have remained above water.  It is thought that the Alene castle was on the hill in the 13th century.  Latvian mountain climbers installed a memorial stone in 1998 opposite Oliņkalns hill.