Tunnel Marathon
Tunnel Marathon is a marathon held in Portsmouth, United Kingdom, in November.
The event is staged at UCAP Bunker, a former Royal Navy underground headquarters that sits about 100 feet below ground, roughly two miles north of Portsmouth. Runners cover the full 26.2 miles on a lapped course through several of the bunker's tunnels, in the same multi-lap style as the organiser's earlier prison and museum marathons.
Headroom varies along the way. Some passages are only about six feet high, so taller runners have to stoop through stretches of around 20 metres, and these low sections come round again on every lap. The setting is underground and enclosed, and the repeated loop makes the course simple to learn.
Who it's for
A solid challenge for committed running athletes.
Good fit if you…
- have done a few events and want a real challenge
Maybe not if you…
- want a big marquee event: this is a smaller, local-scale race
What should you know about Tunnel Marathon?
- Date
- Saturday, 21 November 2026
- Format
- Marathon
How do you register for Tunnel Marathon?
Where does Tunnel Marathon take place?
Portsmouth, United Kingdom
Train near this race
Places to train within 15 km of the start, picked for running.
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