travel northwest for on the Yukon River, except for a few short portages. During this stretch, two hospitality stops are available. The first is from Eagle at Trout Creek. The next is Biederman's Cabin, the former home of Charlie Biederman, one of the last people to deliver mail by sled dog. (The final sled dog mail route was canceled in 1963, and Biederman's sled hangs in the National Postal Museum.) A dog drop site is located from Biederman's Cabin at Slaven's Cabin, a historic site operated by the National Park Service. Some past Slaven's Cabin mushers arrive in Circle, so named because its founders believed it was on the Arctic Circle. (Circle is actually about south of that line.) From Circle, it is to the checkpoint in Central. Mushers follow Birch Creek south until just before Circle Hot Springs. This area, along with the Fortymile stretch, is considered among the coldest on the trail, and mushers are advised to prepare for temperatures. Turning west, they travel through frozen swamps before reaching the Steese Roadhouse checkpoint in Central. In Central during even years, mushers have the option of taking their four-hour rest here or at Mile 101. If they choose to, the three minute start difference will be subtracted from their rest time. Central to Two Rivers From Central to the final (or first, in the Fairbanks–Whitehorse direction) checkpoint in Two Rivers is . Despite the comparative closeness of the checkpoints and the location of a dog drop between them, this is considered the most difficult stretch of dog sled trail in the world. At this point, mushers must climb the two steepest and most difficult mountains on the trail: Eagle Summit and Rosebud Summit. After leaving Central, mushers head west, paralleling the Steese Highway, which connects Central and Circle with Fairbanks. The trail travels through frozen swamps, mining areas, and firebreaks for about . Mushers then encounter the Steese Highway for a second time before crossing several creeks to begin the ascent of Eagle Summit. They eventually climb above the tree line and are exposed to the wind as they continue upward. The weather atop Eagle Summit is harsh as this is a convergence zone between the Yukon Flats to the north and the low ground of the Tanana Valley to the south. A differential in the weather within the two valleys causes high winds and precipitation when there is