The architecturally spectacular Qatar National Convention Centre is the largest exhibition centre in the Middle East. Japanese architect Arata Isozaki, winner of the 1986 Royal Institute of British Architects (RIBA) Gold Medal, has inserted the large glass facade between steel columns that form the branches of two huge Sidra trees. This is a reference to the Sidrat al-Muntaha, an Islamic sacred tree that is believed to symbolise the end of the seventh heaven. Half of the branches are outside and the other half inside the building. Each trunk has four main branches with a diameter of between 23 ft or 7 m (at the base) and 13 ft or 4 m (at the top). The 820 ft (250 m) long steel structures that make up the two trees were manufactured in Malaysia and assembled in Doha. In addition to its therapeutic virtues, which have been known since ancient times, the Sidra tree – an endemic tree in Qatar – symbolises solidarity, determination, hospitality and resilience, given its ability to defy harsh climatic conditions.