Three concrete tower blocks, maze-like walkways and a gorgeous conservatory – the Barbican estate is a stunning brutalist structure, but it’s also much more. Built in the ’60s, it’s a symbol of what housing in London could have been: a utopian sky city with affordable homes rubbing up beside grander ones. Now even the pokiest Barbican flat seems like a mansion (with a price tag to match). But the buildings are still open to all – as is the Barbican Centre. It serves up some of the city’s best culture from its concrete box.