Guildhall Art Gallery is the new kid on the block when it comes to monthly late openings, but it's quickly establishing itself in the cultural calendar. The next event is this Friday (29 June), with the gallery remaining open till 10pm.
This is the only venue in London, perhaps the world, to offer burlesque inside a subterranean Roman amphitheatre. Upstairs, you'll find a string quartet playing classical-style versions of pop songs. A cocktail bar, close-up magician, jewellery-making class and "wandering installation piece" complete the entertainment. And if none of that's for you, simply wander around the impressive collection of canvases, many depicting scenes from London's past. At the very least, you can scowl/genuflect at the Margaret Thatcher statue.
You can also take the opportunity to visit the gallery's latest exhibition Butcher, Baker, Candlestick Maker, which presents artifacts from the holdings of City livery companies.
Entrance and all activities are free, except for the temporary exhibition, which is £5/£3.