Toulouse is a city in southwestern France, near the Pyrenees, in the Midi-Pyrenees region, half way between the Atlantic and the Mediterranean. Toulouse has become a center of aviation and spaceflight in the past 20 years. More than 35,000 of the inner city's 400,000 citizens work in the civil aviation or space industries. The city built on the Garonne river, is on the site of an ancient Roman settlement; even today many of the smaller streets follow their Roman counterparts and many of the red brick buildings are of a pseudo-Roman style. These buildings are also what gives Toulouse its nickname La ville rose (The pink city). In the middle ages, Toulouse was one of the richest cities in France due to the sale of blue coloring (pastel) extracted from woad plants. This monopoly was only broken when the Portuguese began to import Indigo to Europe. Over 50 hotels, mansions, remain witness to the past wealth. The climate in Toulouse is warm in winter increasing to hot in summer, rainfall can happen all year round.