876 roads and bridges: The Islamic World side Travelers also fell prey to highwaymen who lurked on the sides of roads and robbed passersby Crossing streams and rivers could be challenging in medieval Europe Bridges were expensive and difficult to build and fairly uncommon, especially in the early medieval period The landowners who maintained roads were supposed to take care of bridging streams and rivers along the way, but this did not always happen People most often crossed streams at shallow spots called fords, simply walking or driving straight across the stream bottom Fording streams could be dangerous if the water was deeper than usual, the current was strong, or the bottom was slippery In other places boats called ferries would carry people and cargo across rivers for a fee Bridges became more common starting in the late 11th century Bridges were often built on the sites of fords The earliest bridges were made of wood, but as the medieval period progressed engineers became more adept at erecting sturdier stone structures Bridges were prone to various types of damage, such as fire and collapse Major floods destroyed many medieval bridges The most basic type of bridge was a beam bridge The simplest version of this bridge was just a log or plank laid across a stream Travelers walked across it Sometimes people would lay several planks across a stream, using rocks in the streambed as intermediate supports People might also arrange large rocks within the streambed to make stepping-stones across it Beam bridges were inherently weak because they were not supported in the center; the longest distance a single plank or log could span was about 20 feet The wood had to be replaced regularly because it rotted Nevertheless, beam bridges were perfectly adequate for their purposes and they were cheap and easy to construct, so they were quite common throughout medieval Europe In areas with large numbers of boats, people sometimes put together pontoon bridges A pontoon bridge consisted of several boats moored side by side across a river with boards laid across them that formed a surface to walk on The boats were tied to one another to prevent them from drifting and disassembling the bridge This type of bridge could be created and dismantled quickly for temporary needs, but it could also be used as a permanent structure The first bridge over the Grand Canal in Venice was a pontoon bridge called the Ponte Della Moneta built in 1181 on the site of what is now the Rialto Bridge During the later medieval period, arched bridges made of stone became more common Builders used engineering techniques similar to those for building cathedrals to create foundations and arches that could support heavy bridges which rose high over the surface of the water Builders sank wooden pilings deep into the riverbed and then built dams to divert the flow of water while they created concrete pilings to support the structure Stone bridges could be quite large The stone bridge built in the 1370s to span the Adda River in Italy was built on one arch about 240 feet long and 70 feet high London Bridge, built between 1176 and 1209, was 1,050 feet long and supported by 19 stone arches The Ponte Vecchio, which spanned the Arno River in Florence, was built on three arches, each of which was between 88 and 98 feet wide The stone Ponte Vecchio was built in 1345 to replace an old wooden Roman bridge that had been destroyed by a flood in 1333 Building bridges that could permit boat traffic was a challenge for medieval engineers Boats typically could not pass beneath beam bridges, but these structures were often simple to dismantle and rebuild Pontoon bridges likewise blocked the stream and did not permit free boat travel Boats that were not too tall could pass under stone arches For larger boats, one solution was to build bridges that could be lifted when necessary Some canals and streams had drawbridges across them A drawbridge was attached to a hinge on one bank and could be raised and lowered to span the water as needed Drawbridges often formed the entries into castles surrounded by moats The Rialto Bridge was first built in 1250 as two wooden ramps with a center section that could be lifted out to allow ships to pass This wooden structure closely resembled the stone bridge that eventually replaced it in 1591 and that still exists in the early 21st century Bridges were expensive to build and maintain Wooden bridges required more maintenance than stone ones because wood rotted and burned easily The wooden Rialto Bridge, for example, burned in 1310 and collapsed in 1444 and again in 1524 Cities paid for construction and maintenance by levying taxes (the London Bridge, for example, was paid for with a wool tax), charging tolls to those who crossed, and by renting out space on the bridges to merchants The London Bridge, the Ponte Vecchio, and the Rialto Bridge were all covered with apartments and shops and were often packed with shoppers and vendors The Islamic World by Bashir A Kazimee During the Middle Ages, Islamic countries experienced significant growth in all areas of their economies, including commerce, agriculture, and industry Material goods, products, and raw materials for exchange and consumption had to be transported across vast stretches of land along safe and supervised routes to major urban centers To facilitate trade and travel, the rulers in the Islamic world paid particular attention to building and maintaining roads, along with their necessary infrastructures, which connected the thriving cit-