Tier of the Chabet Ilelouïne bridge

Lower tier of the Chabet Ilelouïne bridge. The bridge consists of three tiers:
two of ashlars around a concrete core, and a third tier of concrete poured into
formwork. The lowest tier is an independent bridge, 8 m high, which acts as a
rigid, stable base for the two upper tiers. The two upper tiers are in fact
25 m high piers which are cross-braced by small supporting arches that serve
to inhibit sideward shift of the columns. The whole bridge is tapering upwards
through a series of steps, thus reducing the weight of the upper tiers.