Carmel and Monterey run out of easy onward road and rail links, so San Francisco is the natural last stop before flying home for runners who want a city extension rather than more coastline. April in San Francisco is cool and changeable: mornings often start with fog burning off by midday, and the city's famous microclimates mean it is entirely possible to leave a sunny Mission District and arrive twenty minutes later in a grey, windy Sunset District. Layer accordingly.
Nights One to Three: San Francisco
San Francisco's defining physical fact for a runner on recovering legs is its hills, and they can be genuinely hard going in the days immediately after a marathon. The flat alternative is the Embarcadero, the waterfront promenade that runs along the bay from the Ferry Building past Pier 39 toward Fisherman's Wharf, paved and level for its full length, with the bay on one side and the city's cable car turnarounds and historic piers on the other. It is the obvious first-day option: interesting without demanding a climb.
The Ferry Building itself, at the foot of Market Street, houses a food hall built around Bay Area producers, useful as a low-effort, high-quality food stop without needing a dinner reservation. Fisherman's Wharf and Pier 39, further along the same flat stretch, lean more tourist-facing, but the sea lions that haul out on the pier's floating docks are a genuine, free, low-effort attraction rather than a manufactured one. Golden Gate Park, inland and considerably larger, is flatter than the city's hill districts once you're inside it and offers a slower, greener day for later in the stay, once the legs have had more time to recover. The park runs west almost to the ocean, ending near Ocean Beach, a wide, flat stretch of sand that makes a reasonable low-key finish to a park day without any further climbing required.
The Golden Gate Bridge itself is worth seeing even if walking its full span isn't appealing on tired legs. Crissy Field, on the bay side beneath the bridge, is flat, paved in sections and gives a straightforward view of the bridge from below without the exposed, windy walk across it. Save the bridge crossing itself, if it happens at all, for the last day of the stay rather than the first.
The city has enough range in hotels and restaurants that a general area matters more than a single named property: staying near the Embarcadero or in Union Square keeps the flat waterfront walk and the main transit connections within easy reach, without needing a car for the stay itself.
Getting to San Francisco International Airport (SFO)
San Francisco International Airport sits south of the city and connects directly to the BART rail network, which runs into downtown San Francisco and out to the airport on the same line, making it one of the more straightforward airport transfers on this itinerary without needing a taxi or rideshare.