After the end of the civil war in 1970, Sanaa began to expand outward. This was a period of prosperity in Yemen, partly due to the massive migration of Yemeni workers to the Gulf states and their subsequent sending of money back home. At first, most of the new development was concentrated around central areas like al-Tahrir, the modern centre; Bi'r al-Azab, the Ottoman quarter; and Bab al-Yaman, the old southern gate. However, this soon shifted to the city's outskirts, where an influx of immigrants from the countryside established new neighbourhoods. Two areas in particular experienced major growth during this period: first, the area along Taizz Road in the south, and second, a broader area on the west side of the city, between Bi'r al-Azab and the new avenue called Sittin. A new ring road, built in the 1970s on the recommendation of the United Nations Development Programme, encouraged land speculation and further contributed to the rapid expansion of Sanaa.