It's been several weeks since our last visit to the World Trade Center site. On our return today we were taken with the manner in which different architects handle ventilation at the site. The most obvious example are the two large vent structures that protrude from the west side of the Memorial Plaza. The concrete buildings are a necessary solution to a complicated infrastructure problem. Davis Brody Bond (now Aedas) designed a mesh mask for the concrete structures and workers were putting the finishing touches on south building today. Snøhetta's Museum Pavilion also holds more than 13,000 square feet of mechanical functions, and it too must vent. In the last couple of weeks the protective plastic was pealed off building, and it appears that openings for vents merge into the metallic pattern on the south face of the building. But perhaps the most elegant solution we saw today came as a surprise. Tower 4 has been racing skyward for a while now; we noted the glass facing the plaza went up a few weeks ago. But it was a delight to see how Fumihiko Maki's vertical vents play off reflective glass panels on the buildings south face, bringing much needed light to a dark section of Liberty Street.