We dropped in to the Tate Modern during our last London Photo Walk. The weather was pretty grim so we had to revert to plan B (which was get out of the rain).
It's a fabulous building and one of the most visited landmarks in the UK. Damien Hirst had his long running exhitbion there so the hallways, cafe and book shop thronged with people discussing 'what is art anyway?' which seems to be a favourite topic of people interested in art.
Tripods are not allowed (like in most public buildings) here but Marisol, from Buenos Aries, hit on the great idea of using a plastic cone that was being used to warn visitors of the wet floor. By using a coat wrapped up to make a beanbag shape balanced on top of the cone the camera was solid enough to get a reasonably good shot.
If you are in the London then a visit to the Tate Modern is well worthwhile. It's on the south bank, opposite St Pauls Cathedral.