The oldest stone castle in Latvia is Ikskile bishop's castle (Uexküll). In accordance with the Chronicle of Henry of Livonia construction of this castle started in summer 1185. The castle was built by stonecutters from Gotland next to Ikskile stone church built shortly before - it is the oldest stone building in Eastern Baltic. Nowadays on the island of St Meinhard in the artificial lake of Riga hydropowerplant there still exist remnants of the basement and foundation of church and castle.
Second oldest stone castle has been built nearby few years later - around 1188. It is Vecsalaspils medieval castle, which was built on Martina Island. Nowadays remnants of the castle are under the water of Riga hydropowerplant lake. Most likely there was not built any other stone castle in Latvia in 12th century.
The oldest remnants of medieval castle above the level of soil most likely are parts of Ist court of bishop in Riga (built before 1207), which most likely are included in walls of newer buildings, f.e. in the thoroughfare of pastorate of St John church.
The oldest free-standing remnants of medieval castle above the soil belong to Sigulda castle built in 1207-1209 - although major part of currently visible walls have been constructed later.
Thickest walls - north-western tower of Salaspils medieval castle built in the end of 15th century or beginning of 16th century. Thickness of walls reached 6,5 metres, thick walls enclose rounded room which in turn had diametre of 8 metres. Close nearby there was north-eastern tower with walls up to 5,9 metres thick. Remnants of these walls are not seen - they are either under the water of Riga hydropowerplant lake or below the dam of the lake.
Thickness of walls of the prison in southern tower of Cesis medieval castle is up to 4,7 metres, walls in some other castles of Latvia also exceed 4 metre thickness.
The highest tower of medieval castle nowadays is the main tower of Turaida medieval castle. Initially in the second decade of 13th century it was 30 metres high. Current height - 29,2 metres.
It is not possible to determine whether some other medieval castles of Latvia had other, higher towers. It is known that the massive tower of Ergli medieval castle was more than 24 metres high, main tower of Bauska castle of order is 22 metres high.