Cast Iron Buildings
Masonry walls don't have much shear strength. After all, they're just a bunch of rocks piled one on top of another. It's relatively easy to push them over. For strength, they must be made thick. You can't have many windows, or at least not large ones, and maintain resistance to shear forces such as high winds or battering rams.
These buildings, one 19th-century, one 16th, illustrate the point. Lots of wall, not much glass.
Sometime in the mid-19th Century, cast iron began to replace masonry, allowing designers to open buildings up to admit more light and permit something new for retailers: display windows. Nowhere is this more evident than in Manhattan's SoHo.
I found some cast iron architecture in Madrid; for example, the Mercado de San Miguel.
Not long ago, this place was a bustling hive of small vendors' booths. Currently it is not being used, but I can't imagine that it will remain idle for long.
Most of our buildings in San Miguel de Allende are masonry, and display windows are small. Shops are dark inside, and you have screw up the energy to go inside them if you want a look at the merchandise. In contrast, most of what's inside Madrid's Mercado de San Miguel is visible from the street.
A small cast iron building houses a café on the Paseo del Prado. Diners sitting inside maintain connections with passers-by. No walls to create barriers.
It's an inviting place. The openness of the lacy ironwork makes you feel like you're already half inside the café as you pass by. Why not come all the way and join us?
The ultimate achievements using spidery iron frameworks and glass were the great glass pavilions, of which the Crystal Palace in London was the largest. It was destroyed by fire in 1936, but Madrid's much smaller Palacio de Cristal still stands in Parque del Buen Retiro, just east of the Prado.
Being Spanish, tiles are incorporated into the framework. The shell of the pavilion is almost completely transparent—even the roof.
Like so many Spanish monumental buildings, it's beautifully maintained. The Palacio de Cristal is used today for special gatherings and performances. That it is a working building improves the odds that it will remain a Madrid landmark, and a great place to retire beside on a sunny Sunday.