The inner sanctum of Doñana — the dune systems, the true marismas, the Atlantic beach within the park boundary — is accessible only by booking a place on an official guided tour. These run in purpose-built 4x4 coaches that take groups of around twenty people on four-hour circuits departing from El Acebuche visitor centre, near Matalascañas. The restriction is deliberate and it works: the absence of casual visitors from the core means the wildlife is genuinely undisturbed, and encounters are real rather than performative.
Tours run morning and afternoon, with the morning slot generally better for wildlife. Booking ahead is strongly recommended — they sell out weeks in advance in spring. The guides speak Spanish (some also manage basic English) and are very good at spotting things most visitors walk past: a fallow deer herd browsing in the scrub, a red deer stag standing broadside at a clearing edge, a short-toed eagle perched in a pine. Wild boar are almost guaranteed. In the right season, the marismas section of the route produces flamingoes, spoonbills, and a bewildering number of ducks.