By around 1300 true domes and arches with voussoirs were being built; the ruined Tomb of Balban (d. 1287) in Delhi may be the earliest survival. The Alai Darwaza gatehouse at the Qutb complex, from 1311, still shows a cautious approach to the new technology, with very thick walls and a shallow dome, only visible from a certain distance or height. Bold contrasting colours of masonry, with red sandstone and white marble, introduce what was to become a common feature of Indo-Islamic architecture, substituting for the polychrome tiles used in Persia and Central Asia. The pointed arches come together slightly at their base, giving a mild horseshoe arch effect, and their internal edges are not cusped but lined with conventionalized "spearhead" projections, possibly representing lotus buds. Jali, stone openwork screens, are introduced here; they already had been long used in temples.