In a country like Scotland, with varied, often rugged topography, and a climate that is frequently harsh, transport can still be difficult even with modern technology. The principal form of investment in overland communication before the eighteenth century was bridge building. Something of the character of these early roads can be gained from surviving traces in the landscape although the precise dating of old roads is difficult. By the end of the eighteenth century over 3,000 miles of turnpikes were in operation in Scotland and a comprehensive network of improved roads ran through most parts of the Lowlands as far north as Aberdeen. The most famous programme of road construction in eighteenth-century Scotland was the building of a network of military roads, mainly in the Highlands. The canals which were built in Scotland in the eighteenth and early nineteenth centuries were mainly short through routes crossing peninsulas or serving as feeders into the main estuaries.