Quuen Mary's Rose Garden offers a delight to rose maniacs. Below photograps were taken end of May - looks like this is the best timing to visit this rose garden in London. Located in Regents Park. Queen Mary's Rose Garden is one of the greatest formal rose gardens, with about 400 different varieties and more than 60,000 plants. It was founded in 1828 and was originally called the gardens of the Royal Botanic Society.