The Chicago Marathon course

Out of Grant Park on Columbus Drive with the Aon Center over your shoulder, a swing onto Grand Avenue, and a river bridge before the first mile is done. Everything feels easy and crowded at once, which is the worst possible combination for judging effort.

Grand to State and Dearborn past Marina City, over the water a second time. Your watch is working between towers here, so trust the painted mile markers and not the split it hands you.

The LaSalle canyon with stone on both sides and the Board of Trade closing off the end of it. Wide, straight and fast feeling: this is the mile to deliberately underrun.

North on LaSalle Drive, out of the Loop and back across the river one more time. The buildings step back, the sky opens, and the GPS starts telling the truth again.

Past Moody Church the road bends onto Stockton Drive and Lincoln Park opens in front of you. More room, cleaner air, and a real temptation to spend something you will want later.

Fullerton Parkway and Cannon Drive through the park. This is the largest single drop the course has anywhere, which on Chicago means you will barely feel it: take the free speed, do not chase it.

Cannon Drive out to Lake Shore Drive and Sheridan Road with the lake off to your right. Wind is the only variable out here, and it either gives or it does not.

The northernmost point of the whole loop, on Lake Shore Drive and Sheridan. You are as far from Grant Park as this course ever puts you, so run it by feel rather than by ambition.

Broadway through Lakeview, pointed south for the first time all morning. The street is narrower, the field is tighter, and the race finally feels like it has started.

A long southbound straight, Broadway into Clark Street, with very little to look at. Use the quiet: add up your first ten miles and see whether they match the plan you wrote.

Clark over to Sedgwick, edging back toward Old Town. Nothing on this road will slow you down, and on this course that is the whole problem.

Old Town arrives on Wells Street after the turn off North Avenue. The skyline is back in front of you now and it is still a long way off.

Wells Street south with two river bridges inside a single mile. Shorten your stride across the decks, keep your eyes up, and do not let the crossings chop your rhythm.

Halfway comes on Wacker with Willis Tower straight overhead and Adams Street waiting past the last bridge. Whatever the half split reads, this course does its deciding after this point.

Adams Street runs dead west through the West Loop and does not stop. Long, flat and featureless: pace drifts on miles like this without ever asking permission.

Adams to Jackson and out to Damen, with the United Center standing off to the north. This is the westernmost turn of the day, and everything after it points back toward the lake.

Dead straight back east on Jackson Boulevard. This is where a marathon quietly settles what kind of day it is going to be.

Halsted through Greektown, then the turn onto Taylor Street. Eighteen on a flat course arrives with no warning and no excuse attached.

Little Italy on Taylor Street, then south onto Loomis. Twenty is next, and you should already know whether this pace is yours to keep.

Eighteenth Street cuts into Pilsen after the jog down Loomis and Halsted. The street tightens and the neighbourhood gives more than it takes, so use it, because the next mile will not.

Three turns in a mile: Cermak, Canalport, and a bridge on Halsted pointed at Chinatown. Broken rhythm at exactly the point where tired legs stop paying attention.

Under the gate on Wentworth through Chinatown, then out onto 26th Street. The turns end, the field spreads, and the road ahead gets very plain.

Twenty-sixth Street crosses Michigan on the far south end of the loop. There is nothing out here to distract you, which makes the rest of this a straight negotiation with your legs.

Indiana Avenue, a stretch of 35th Street, and then Michigan Avenue for good. Just over two miles left and every one of them in a straight line.

Michigan Avenue, flat and unbroken, with the skyline growing at the end of it. It looks close from a very long way out, and that is exactly why this mile costs so much.

The last turn off Michigan is onto Roosevelt Road, the one honest rise on the entire course, saved for mile 26. Over the top, hard right onto Columbus, and Grant Park finishes what it started.