The development of masonry led to a widespread use of stone in simple structures such as fortifications, but due to the weight and cumbersome nature of stone blocks, more complex structures had to be made of simpler materials. The need for the widespread use of more durable and permanent materials eventually became apparent, forcing ancient artisans to learn new techniques. The biggest problem to overcome was finding a stable way to span the distance between two upright columns or walls using stone blocks. To solve this problem, fundamental architectural elements such as the arch and vault evolved. These basic construction techniques allowed larger and more elaborate buildings to be created from stone and mortar. Many of the buildings erected by these early builders are still standing, a testament to the sound construction techniques employed in their construction.