The Classic best seller,
one-prim bridge,
that apart from beauty, can also be actually used for what its made for :)
Sculpted prims suffer from inaccuracy when it comes to collisions and walking, because they all use the same bouncing collisions map, regardless of their actual shape. This forces all builders to set them as phantom, and use other prims, transparent, as a walking surface ( usually called walk helpers ). The design of this bridge is such that can be used for walking, as is, with very good accuracy!