Well, it is closed to vehicle traffic. The occasion is the annual BUPA Great Winter Run on the first Saturday of the year.
There are junior and senior races as well as the international cross country which, as usual, will be televised.
For me it is the 5k - once round Arthur's Seat - and trying to beat my time last year of 28:00 minutes. I'll be running for the Bethany Homeless Charity.
Details of the race schedules can be seen here.