Its imprint on the Delhi skyline as distinctive as it gets, the Hall of Nations at Pragati Maidan is widely seen as an iconic representation of modern Indian architecture. The space-frame octahedron structure, with trusses splayed out in visually dynamic lines, was built in 1972 as part of celebrations to mark 25 years of India’s independence and to mark the country’s arrival as a global exhibition space for industrial goods. Its architect, Raj Rewal, opted for reinforced concrete instead of tubular steel frames then popular in American and European architecture, and labour-intensive construction methods instead of technology-driven ones. The logic was simple: steel was scarce and expensive in India but labour was abundant.