British forces under Frederick Roberts on 5 June 1900 and the conflict was ended in Pretoria with the signing of the Peace of Vereeniging on 31 May 1902 at Melrose House. The Pretoria Forts were built for the defence of the city just prior to the Second Boer War. Though some of these forts are today in ruins, a number of them have been preserved as national monuments. Union of South Africa The Boer Republics of the ZAR and the Orange River Colony were united with the Cape Colony and Natal Colony in 1910 to become the Union of South Africa. Pretoria then became the administrative capital of the whole of South Africa, with Cape Town the legislative capital and Bloemfontein served as the judicial capital. Between 1910 and 1994, the city was also the capital of the province of Transvaal. (As the capital of the ZAR, Pretoria had superseded Potchefstroom in that role.) On 14 October 1931, Pretoria achieved official city status. When South Africa became a republic in 1961, Pretoria remained its administrative capital. Geography Pretoria is situated approximately north-northeast of Johannesburg in the northeast of South Africa, in a transitional belt between the plateau of the Highveld to the south and the lower-lying Bushveld to the north. It lies at an altitude of about above sea level, in a warm, sheltered, fertile valley, surrounded by the hills of the Magaliesberg range. Climate Pretoria has a subtropical monsoon climate (Köppen: Cwa) with long hot rainy summers, and short, dry and mild winters. The city experiences the typical winters of South Africa with cold, clear nights and mild to moderately warm days. Although the average lows during winter are mild, it can get cold due to the clear skies, with night time low temperatures in recent years in the range of . The average annual temperature is . This is rather high, considering the city's relatively high altitude of about , and is due mainly to its sheltered valley position, which acts as a heat trap and cuts it off from cool southerly and south-easterly air masses for much of the year. Rain is chiefly concentrated in the summer months, with drought conditions prevailing over the winter months, when frosts may be sharp. Snowfall is an extremely rare event; snowflakes were spotted in 1959, 1968 and 2012 in the city, but the city has never experienced an accumulation in