You thought you knew how to picnic until you visited the Dallas Arboretum. No other swath of greenery boasts more professional picnickers per square foot. Come to think of it, no other spot in Dallas offers this much greenery or natural beauty. No wonder so many people commit an afternoon here, grazing al fresco while sitting on Grandmother's heirloom quilt. You could bring a couple of sandwiches and some sodas from the convenience store, but you will be made to feel very small. Here, the picnic baskets are the size of Volvos and everyone worth their weight brings wine. Sandwiches are for sissies, and spreads look like the buffet tables filled with exceptional food. And why not picnic here? Even on the most crowded days it's not hard to find a space — a small square of greenery where you can sit and relax and ponder finer things.