Bank of America Chicago Marathon

{
  "guide": [
    "GPS lies in The Loop and around Lincoln Park. Run by feel, not by watch — the course is exactly 42.195 km if you run the tangents.",
    "Wind off Lake Michigan can hit at km 5–10 and km 30–35. Find a pack and tuck in.",
    "Save legs for the Roosevelt bridge. It's small but at km 41.5, it feels like Heartbreak Hill.",
    "Best PR opportunity in the World Majors after Berlin."
  ],
  "profile": "Pancake flat. Loop course through 29 neighborhoods, starting and finishing in Grant Park. The only \"hill\" is the Roosevelt Road bridge in the final 400 m.",
  "terrain": "flat",
  "keyFeatures": [
    "km 0 — Grant Park start. Crowded — first 2 km are cramped.",
    "km 13 — Lincoln Park. Watch for the GPS deadzones under tall buildings — pace cues drift.",
    "km 30 — Pilsen and Chinatown. Loud crowds, you'll surge involuntarily.",
    "km 41.5 — Roosevelt Road bridge. The single climb of the day, ~12 m, right before the finish."
  ],
  "elevationGain": 30,
  "elevationLoss": 30
}