Biržuvėnai mound is located on the right bank of Virvyčia. Used in the IX – XII c.
The north-western part of the site was washed by ropes changing the furrow. It is believed that this mound served as a pier. There are also traditional claims that show that this mound was a fortification-type fortification, in which the locals, in case of danger, hid their possessions and property and defended themselves from enemies.
In the highest eastern edge of the site and in the embankment there is a pit marking the site of the brick Gorskiai chapel, which was destroyed during the First World War. It is believed that during the Protestant Reformation, a Protestant (Evangelical Reformed, Calvinist) church stood on a mound on the site of the Gorskiai Chapel. Calvinists were popularly called bambizai, so the mound got the name Bambizkalnis. Biržuvėnai mound is also called Koplyčkalnis.