The topography of Macedonia features a mountainous landscape covered with deep basins and valleys. There are two large lakes, each divided by a frontier line. Approximately 24% of Macedonia's land is arable. Natural resources include chromium, lead, zinc, manganese, tungsten, nickel, low-grade iron ore, asbestos, sulphur, and timber. Macedonia's natural environment suffers from a high seismic hazard and air pollution from metallurgical plants.