At the weekend I took part in the 3rd London City Race. Every year it has been growing, and this year there were more than 750 people including more than 100 overseas runners taking part. The weather was perfect, and many people combined the race with a weekend in London, either sightseeing, or taking part in the race on Sunday as well (or both).
The race itself was really fun - a mixture of high speed, high concentration orienteering, and some parts in for the tourists! We warmed up over Tower Bridge, started at the Tower of London, ran past St Paul's Cathedral, the Gherkin, had a route choice over either Millenium Bridge or London Bridge, ran along the South Bank, past Borough Market, and even through London Bridge Underground station! The finish was on the bank of the river Thames, right by City Hall. And there were a lot of really difficult controls on multiple levels - lots of bridges and underpasses.
If you haven't been - make sure you go next year!