Frederick Law Olmsted’s Emerald Necklace, a chain of parks that stretches throughout the city, is, more than a century after its creation, one of Boston’s enduring gems. Yet even a masterpiece needs a bit of help. Enter the 15th annual Party in the Park. Hosted by the Emerald Necklace Conservancy to help underwrite park improvements and upkeep, this year’s fiesta takes place at Olmsted’s Franklin Park on May 31 beginning at 11 a.m. Filled with fine cuisine, award presentations, raffles and plenty of creative, colorful hats, this is one of the most anticipated social events of the spring. Tickets can be purchased at 501auctions.com/pip2018.