Some of the most impressive Roman ruins I’ve seen were actually in Spain, or Hispania as it was known then. In fact, this one hardly counts as a ruin, considering that it has been restored at various times over the years and was used for its intended purpose until the mid-19th century. This aqueduct, built around the 1st century AD, is one of the symbols of Segovia, Spain. Seen here in 2006, it has two beautiful layers of arches, one large on the bottom and one smaller on top.
You can see the layers of unmortared bricks in this closer shot. The niche holds a statue of the Virgin Mary, which the Internet tells me may be la Virgen de la Fuencisla, the patron saint of Segovia.
You can find more layers filled at the original Lens-Artist challenge.
You can also check out some layers of cliff-nesting seabirds from a previous WPC: Layered.