a number of ancient and medieval ruined cities built in a unique dry stone style. Among the most famous of these are the Great Zimbabwe ruins in Masvingo. Other ruins include Khami Ruins, Zimbabwe, Dhlo-Dhlo and Naletale. The Matobo Hills are an area of granite kopjes and wooded valleys commencing some south of Bulawayo in southern Zimbabwe. The hills were formed over two billion years ago with granite being forced to the surface, then being eroded to produce smooth "whaleback dwalas" and broken kopjes, strewn with boulders and interspersed with thickets of vegetation. Mzilikazi, founder of the Ndebele nation, gave the area its name, meaning 'Bald Heads'. They have become a tourist attraction because of their ancient shapes and local wildlife. Cecil Rhodes and other early white colonists like Leander Starr Jameson are buried in these hills at World's View. Water supply and sanitation There are many small-scale successful water supply and sanitation programs, but there is also a general lack of improved water and sanitation systems for the majority of Zimbabwe. According to the World Health Organization in 2012, 80% of Zimbabweans had access to improved, i.e. clean, drinking water sources, and only 40% of Zimbabweans had access to improved sanitation facilities. Access to improved water supply and sanitation is distinctly less in rural areas. There are many factors which continue to determine the nature, for the foreseeable future of water supply and sanitation in Zimbabwe. Three major factors are the severely depressed state of the Zimbabwean economy, the reluctance of foreign aid organisations to build and finance infrastructure projects, and the political instability of the state. Science and technology Zimbabwe has relatively well-developed national infrastructure and a long-standing tradition of promoting research and development, as evidenced by the levy imposed on tobacco-growers since the 1930s to promote market research. The country has a well-developed education system, with one in 11 adults holding a tertiary degree. Given the country's solid knowledge base and abundant natural resources, Zimbabwe has great growth potential. Zimbabwe was ranked 113rd in the Global Innovation Index in 2021, up from 122nd in 2019. To achieve its growth potential, Zimbabwe will need to correct a number of structural weaknesses. For instance, it lacks the critical mass of researchers needed to trigger innovation. Although the infrastructure is in place to harness research and development to Zimbabwe's socio-economic development, universities and research institutions lack the financial and human