Bilbaoで最も古い樹木はどれですか。
Nobody can name Bilbao's oldest tree with any confidence. Three of the four here, the Albia planes, the Misericordia garden's centenary trees, and the Dona Casilda horse chestnut, are all described only as over a century old by the local sources that mention them, with no measurement, no planting record and no ranking between them. The widest span belongs to the Misericordia garden, whose romantic layout dates to 1872, but that is a garden's founding date, not a proof of any one tree's age, so this page will not promote it to a false answer. The fourth tree, the Deusto bald cypress, carries no age claim of any kind. If you can date any of these four from a photograph, a planting record or a park archive, tell us and this answer will change.
Bilbao has no usable open register of protected or remarkable trees. A regional decree covering the Basque Country's singular trees exists in law, but its published dataset is a dead link, and the city's own municipal tally of roughly 3,000 specimens has no public coordinates attached. So every tree on this page comes from ordinary web research: local newspapers, tourist guides and Wikipedia, none of them built for dating or measuring an individual trunk. That shows in what this page can and cannot say. Three of the four trees are described only as centenario, over a century old, by sources that agree on the phrase without ever explaining how they arrived at it; one travel page's wording for the Dona Casilda chestnut matches another closely enough that they likely share one original source rather than confirming it independently. None of the four carries a girth, and only one has an individual measurement at all, itself unverified against a second source. Two of the four are gardens known for many old trees rather than one named specimen, and this page says so rather than inventing a single tree to point at. Location pins are park-level throughout, not tree-level.