There is still time to sign up for a 20-mile obstacle course around the grounds of Burghley House.
Rat Race Dirty Weekend will take place around Burghley on Saturday next week.
About 5,500 people have already signed up either for the full course or the 13-mile version.
The race will be followed by a music festival, with headliners Ocean Colour Scene supported by a number of local bands.
Runners can still sign up until Wednesday and tickets for the festival, costing just £35 for a night of music and two nights’ camping, will be on sale up until the day of the race.
A spokesman for the event said: “The final stage of preparations are under way and the construction team are building the last zones ready for the May 11.
“We’ve got all our volunteers ready to ensure the runners have a fantastic and safe time on our colossal course and we’re looking forward to all 5,500 ‘Muckers’ taking on our monster obstacles before celebrating with a pint or four in our huge beer tent.”
Full details, including previews of the huge obstacles and details on how to sign up, can be found at www.ratracedirtyweekend.com