The 2-dimensional Lyness map is a 5-periodic birational map of the plane which may famously be resolved to give an automorphism of a log Calabi–Yau surface, given by the complement of an anticanonical pentagon of $$(-1)$$
(
-
1
)
-curves in a del Pezzo surface of degree 5. This surface has many remarkable properties and, in particular, it is mirror to itself. We construct the 3-dimensional big brother of this surface by considering the 3-dimensional Lyness map, which is an 8-periodic birational map. The variety we obtain is a special (non-$${\mathbb {Q}}$$
Q
-factorial) affine Fano 3-fold of type $$V_{12}$$
V
12
, and we show that it is a self-mirror log Calabi–Yau 3-fold.