Most of the circuits currently in use are specially constructed for competition. The current street circuits are Monaco, Melbourne, Singapore, Sochi and Baku although races in other urban locations come and go (Las Vegas and Detroit, for example) and proposals for such races are often discussed—most recently New Jersey. Several circuits have been completely laid out on public roads in the past, such as Valencia in Spain, though Monaco is the only one that remains. The glamour and history of the Monaco race are the primary reasons why the circuit is still in use, even though it does not meet the strict safety requirements imposed on other tracks. Three-time World champion Nelson Piquet famously described racing in Monaco as "like riding a bicycle around your living room".