Rafael Guastavino. The interior of the crossing includes four massive granite arches, which in the original Heins & LaFarge design were originally intended to support the massive tower above it. When completed in 1900, the arches were described as the "crowning glory" of Morningside Heights. During the time that the nave remained incomplete, temporary walls were placed within the arches so that services could be held in the crossing. Above the crossing is a domed roof, which was meant as a temporary covering until the tower above the crossing was built. It was completed within fifteen weeks between May and August 1909. The dome is shaped like a saucer, and consists of several overlapping layers of Guastavino tile, which support themselves around the dome's center upon their own weight. The pendentives, or triangular areas between the circular dome and the corners of the arches, are thick; the thickness of the dome itself ranges from on top to at the bottom. Compared to conventional ceilings, the tiles saved money because they did not require temporary supports when they were installed. For added strength, metal rods were included in the dome's shell. The dome was originally intended to be temporary. Cram had proposed three plans for the structure above the crossing: a steeple, a square tower rising above the crossing floor, and then a slim spire. None of these plans were realized. A three-year renovation project from 2019 to 2022 repaired cracks in tiles, patched concrete, added new protective materials, and built a new copper dome over the crossing. Basements Directly below the crossing is the basement, which contains the crypt, now used as a storage area. The items stored in the crypt include artifacts such as pieces of the destroyed Pennsylvania Station and World Trade Center, as well as wooden angels, plaster gargoyles, leadlights, antique furniture, and a single-file line of saints. The crypt also includes objects such as a large fossil and a massive crystal of quartz, both of which were relocated to the crypt after the 2001 fire. Along either side the basement are rooms, each named after the chapels that they are located under. In the 1980s, the crypt was also home to the Cathedral Works Company, which sold textiles. The crypt also formerly contained the Tiffany Chapel, created by jewelry designer Louis Comfort Tiffany. Originally exhibited at the World's Columbian Exposition in 1893, it was then acquired