Pretoria's main sights are concentrated in two clusters. In the city centre, Church Square is the historic heart — flanked by the Palace of Justice and the statue of Paul Kruger — with the Kruger House, Melrose House, and the Ditsong National Museum of Natural History all within walking distance. A short drive east, the Union Buildings sit on Meintjieskop hill above the city with Nelson Mandela's enormous bronze statue looking out over the amphitheatre lawns. The Pretoria National Botanical Garden (out in Brummeria) holds 50 hectares of indigenous South African flora and is a good retreat from the city. South of the centre, the Voortrekker Monument on Monument Hill is a loaded but unmissable piece of Afrikaner heritage, with sweeping views from the dome. Directly opposite it, Freedom Park is the post-apartheid counter-memorial built on the adjacent hill. For families, the National Zoological Gardens on Boom Street is one of the best zoos on the continent.