The old gateways of Spain's capital, Puerta de Alcalá and Puerta de Toledo, were built in the late 18th to early 19th centuries to mark the eastern and southwestern boundaries of the city's main roads. Their contemporary counterpart, Puerta de Europa, was completed in 1996 as a joint project between American and Spanish architectural firms. Reflective of Madrid's evolution from an old kingdom to a modern city, the "Gate of Europe" does not have its predecessors' granite build nor their neoclassical arches. And, unlike the older puertas, Puerta de Europa is also a functional corporate space. Twin steel-and-glass towers form a single, implied gateway leading into the northern end of Madrid's business district. Each building has a vertical of 374 feet (26 floors) with a 15 degree incline toward its other half. This sideways tilt put the Puerta de Europa on the map as the world's first leaning high-rise office buildings.