The SeaGull Century in Salisbury MD is a long-running annual event that I do every now and then. This past year my Wahoo Elemnt said 104 miles and 450 feet of climbing. The only hills are the bridge to the Chincoteague beach rest stop near the 50 mile mark(which you do twice) and one highway overpass towards the end. The rest is pretty much tabletop flat - if you aren't pedaling you aren't moving...