An open international ideas competition has been launched to reinvent the ruined Red Sands sea fort in the Thames Estuary, off the Kentish coast. The iconic structure – which was one of several offshore installations designed by Guy Maunsell during World War Two – has been unused since 1956. Organised by Seville-based ‘Rethinking Architecture Competitions’, the contest seeks proposals to transform the fort into a new observatory. The Red Sands base was constructed in 1943 and originally featured anti-aircraft batteries. The seven raised structures were originally connected by walkways which have not survived. The first prize winner – set to be announced on 1 May – will receive around £2,300. The deadline for entries is 30 March. Text: Architects’ Journal