On 11 September 1973, the Kenyatta International Conference Centre KICC was open to the public. The 28-storey building at the time was designed by the Norwegian architect Karl Henrik Nøstvik and Kenyan David Mutiso. It is the only building within the city with a helipad that is open to the public. Of the buildings built in the Seventies, the KICC was the most eco-friendly and most environmentally conscious structure; its main frame was constructed with locally available materials gravel, sand, cement and wood, and it had wide open spaces which allowed for natural aeration and natural lighting. Cuboids made up the plenary hall, the tower consisted of a cylinder composed of several cuboids, and the amphitheater and helipad both resembled cones. The tower was built around a concrete core and it had no walls but glass windows, which allowed for maximum natural lighting. It had the largest halls in eastern and central Africa.