There are twelve thousand cedars in the avenue. The Nikkō cedar avenue runs for around thirty-seven kilometres in total, with something like twelve thousand trees along the highways leading to the shrines and temples. It was planted over many years by Matsudaira Masatsuna and his son Masanobu, as work that could not be completed within one lifetime and was handed from father to son partway through.

The avenue carries two designations at once, as a special historic site and as a special natural monument, and in 1992 it was recognised as a world record for length. Along the roadside are yōkan shops, inns and souvenir sellers, and that row continues without a break into the approach to the shrines themselves, so the commercial street and the sacred approach are the same piece of road. The Tōbu line runs here directly from central Tokyo, the work available is tourism and lodging, and the roads ice over through the winter months, which shapes the season more than the visitor numbers do.

An avenue is infrastructure whose planter never sees it finished. Cedars take decades to grow tall enough to shade a highway or break the wind across it, which means the decision to plant was, unavoidably, an investment made on behalf of people not yet born — and it had to be renewed, season after season, by someone who would also not see the result. Twelve thousand is not really a count of trees at all. It is a measure of how many consecutive years that decision went on being made by somebody, and of how unusual it is for an intention to survive that long inside a family.