In early sources the Hill of Three Crosses was called the Crooked Hill or the Bald Hill. Standing on the right side of the Vilnia, near its confluence with the Neris, the hill rises 162 m above sea level. To the south and south-west it is bordered by the valleys of the Vilnia and the Neris; to the south and east a valley separates it from Bekešas Hill and Table Hill, and to the north-east lies a hollow known as the Valley of Songs. The slopes of the hill are quite steep, and on top there is a plateau 200 m long and 100 m wide, in the north-western part of which the Three Crosses monument now stands. In 1956 the archaeologist Adolfas Tautavičius discovered traces of a 13th–14th-century homestead on the north-eastern slope of the Hill of Three Crosses. The researchers R. Batūra, A. Tautavičius, N. Kitkauskas, S. Lasavickas, V. Daugutis and others put forward the hypothesis that the third defensive castle of Vilnius, called the Crooked Castle, may have stood here. It was burnt down during the conflict between Vytautas and Jogaila in 1390 and never rebuilt. During archaeological research carried out by V. Daugutis in 1989, the remains of wooden buildings, hearths and pottery shards were found. In the 1830s a military fortress was built in Vilnius on the castle grounds, and a system of defensive works was set up on the Hill of Three Crosses. The Vilnius fortress was finally abolished only in 1878.