What a unique event!! Not so much the route as what's on the route. A half marathon made up of two out and backs on public foot paths, so far not so inspiring? How about each leg has two tunnels to run through. Located in Bath, disused railway tunnels of the Somerset and Dorset line, closed in 1966 and then re-imagined as a shared walking/cycle route by Sustrans in 2013. Dimly lit, fairly narrow (think 5 or 6 people side by side), and coooool! the first tunnel is about 400m and the second about 1 mile. With the out and back nature you will be visiting each tunnel 4 times spending a good proportion of the race underground. This is what makes this race unique and awesome. 

The race organisation is Slick (with a capital S). Park and Ride a couple of miles from the start, frequent buses drop you right at registration. Grab race number - 1 minute, drop your bag - 30 seconds! easy. Races go off in waves 10mins apart and when you see the tunnels you realise why. Its a well organised tactic by Relish Running to reduce bunching. 

The route is easy to navigate, there are always people around, and the scenery out of the tunnels is mainly tree lined disused railway. 

The medal is one of a set which encourages you to come back and have a crack at other races. Other finish line goodies include energy bars, fruit, haribo etc. 

Its a fab race which will appeal to all. Word of warning though, the organisers bill this as fast and flat. Flat is relative, this is hilly Bath after all. I registered about 700ft of elevation so not really flat, but i'll agree it's not hilly as such!

This race is well worth a look