Inspired by the legendary botanical gardens in Padua where the Medicis plotted the untimely, frothing ends of their enemies, an English duchess created this garden, dedicating it entirely to flora which are deadly and/or narcotic. Behind big black gates, the carefully curated garden contains about 100 legendary killers like Atropa belladonna (deadly nightshade), Strychnos nux-vomica (strychnine), and Conium maculatum (hemlock). Guides explain their deadly properties while keeping ne'er-do-wells and curious children away from the plants, warning them: "Do not touch any of the plants, don't even smell them. There are plants here that can kill you."

atlasobscura.com
alnwickgarden.com
thepoisongarden.co.uk