'Mastaba' by artist Christo can be seen with its reflection of colour in The Serpentine. Taken at 20:18pm. The Mastaba is a 20m high installation on the Serpentine lake made up of 7,506 horizontally stacked barrels on a floating platform. It takes the form of an ancient mastaba, a type of rectangular Egyptian tomb with two sloping sides leading to a flat roof. ? Nigel Howard / Evening Standard / eyevine