Many of Tehran’s problems stem from its rapid growth. Tehran is thus one of the largest and fastest growing cities in the Muslim world. The old core of Tehran is some twenty kilometers from the foot of the Alburz Mountains, on an east-west road at a point where the road divides into two on either side of the foothills. Tehran’s site, size, and layout have also created other environmental problems. The problems of Tehran have their roots in the period before the founding of the Pahlavi dynasty in 1925. Despite its rapid growth, Tehran had comparatively few shantytown settlements, though numbers of immigrants did occupy the extensive abandoned brickworks, living there as troglodytes. Much of the trends and policies continue under the Islamic republic, though in a different form and at a much reduced scale. In 1965, a High Council for City Planning was created, charged with guiding the preparation of master plans for Iranian cities.