Development of the castle's restoration projects is mainly based on materials obtained in archaeological excavations. The first non-professional researches in the Bauska Castle ruins took place in 1874 under supervision of the historical object's owner of that time, the Count P. Lieven. The found antiquities were delivered to the Museum of the Courland Province in Jelgava.

Due to the initiative of the Director of the Museum of Regional Studies and Art of Bauska, L. Liepa in the 1960-ties removal of the construction waste began in several premises of the Bauska Castle, and later archaeological researches were conducted in the Order Castle's territory. The yard's pavement was dug out; a large amount of antiquities, stone forgings, stove tiles, fragments of pottery, as well as samples of construction materials was found.

Starting from 1976 extensive archaeological excavations began in the castle and continued up to 1992. In cooperation with the Museum of Regional Studies and Art of Bauska (later – with the Bauska Castle Museum established in 1990), the investigation was carried out by the Doctor of History, A. Caune. The Bauska Castle Museum’s specialist J. Grūbe conducted later archaeological excavations for several seasons.

Investigations found that in the Early Metal period (about 1500 years B.C.) a fortified settlement of the Balts was located on the bank of the river Mēmele in the location of the Bauska Castle. During excavations, a part of the subterranean building with a fireplace was uncovered; bone decorative pins and pieces of the scratched pottery were found. In several places of the castle a cultural layer of the Iron Age (2nd - 12th century AD) containing pieces of handmade pottery was discovered. Excavations gave an idea about the eastern forepart of the Order Castle. During the investigation the layout of the Duke's residence part of the castle, sizes of the earth fortification structures and construction time were specified.

Archaeologists obtained 2886 antiquities, about 10,000 fragments of stove tiles, 9000 fragments of dishes and 56 samples of construction materials in the castle's territory.

The collection contains more than 300 coins. Most of them were coined in the coin forges of Livonia and Riga in the middle and second half of the 17th century – during the rule of the Kings of Sweden Charles X Gustav and Charles XI, and the Queen Kristina. From those coins forged in the Duchy of Courland, schillings coined during the rule of the Dukes Gotthard and Jacob Kettlers have been found in the Bauska Castle. Also 15th – 17th century coins of the Livonian Order, Archbishops of Riga, bishops of Tharbata and Ösel – Wiek, the Free City of Riga, Poland, Lithuania, Sweden, as well as ducats coined in the unified Provinces of the Netherlands between the 16th and 17th century have been discovered.

Antiquities can be divided in three groups – items related to military conflicts (an arbalest "nut", arbalest arrowheads, cannon fragments and balls, grenades, parts of musket and fusil mechanisms, flints, iron and lead bullets, etc.), samples of construction materials and architectural details (stove tiles, stone forgings, bindings, window panes, fragments of their frames, etc.), tools and household objects (millstones, chisels, files, knifes, spoons, a chessman, draughtsman, barrel taps, fragments of Dutch pipe-bowls and pipe-stems, etc.).

The most valuable are the collection of stove tiles of the period from the end of the 15th century to the beginning of the 18th century and the collection of decorative stone forging made at the end of the 16th century.

The materials of archaeological excavations conducted from 1976 to 1982 in the Bauska Castle are stored in the Department of Archaeology of the Latvian National History Museum. The antiquities found during the later investigations, as well as materials obtained in the 1960-ties and 1970-ties are stored in the Bauska Castle Museum.

Created – Hofmanstudio