Msheireb Properties announced on Saturday that it had appointed a US-based firm to act as lead consultant for phase 4 of the $5.5bn Msheireb Downtown mega project in Doha. Hellmuth, Obata + Kassabaum (HOK) was chosen from a group of internationally renowned architectural firms competing to undertake the design development contract, Msheireb said in a statement.Phase 4 of Msheireb Downtown comprises 135,000 sq m of mixed-use development across 12 buildings that will include commercial, retail, healthcare, residential, a 4-star hotel, civic buildings and public spaces.Issa M Al Mohannadi, CEO of Msheireb Properties, said: \"Msheireb Downtown is fundamentally rooted in Qatar\'s heritage but simultaneously seeks to accentuate modern environmental management and international standards in sustainability through its groundbreaking architectural and design techniques. \"We believe HOK is an ideal partner to help fulfill our vision and we are enthusiastic to have them on board for our Phase 4 design.\"HOK has been involved in the successful planning and design of many mixed-use developments throughout the Middle East and worldwide. Msheireb Downtown, the world\'s first sustainable downtown regeneration project, is being built on a 31 hectare historical site of downtown Doha. The project aims to transform the old commercial and business district into the vibrant, cohesive and culturally active city centre. From / Arabian Business News