When Charles Darwin and the Beagle crew ascended the Río Santa Cruz in 1834, swift currents beyond Isla Pavón obliged them to walk the shore and drag their boats on lines, limiting their progress to about 10 miles per day.
Twenty-five years later, naval explorer Luis Piedra Buena first raised the Argentine flag where his namesake town now stands; Perito Moreno ascended partway in 1879, and territorial governor Ramon Lista made the first arduous steamer ascent in 1890, all the way to Lago Argentino and Lago Viedma.
Piedra Buena (pop. 4,175) has little to see, but its services makes it worth a lunch break or even an overnight stay before seeing Parque Nacional Monte León [1]. On the Río Santa Cruz’s north bank, it’s 127 kilometers south of Puerto San Julián [2] and 235 kilometers north of Río Gallegos [3] via RN 3. About 45 kilometers south, westbound RP 9 provides a bumpy motorist’s or cyclist’s shortcut along the Río Santa Cruz valley to El Calafate [4].
While the town is nondescript, Isla Pavón, reached by a turnoff from the bridge over the Río Santa Cruz about three kilometers south of the highway junction, is a wooded beauty spot that’s popular for fishing; a small museum honors Piedra Buena’s efforts.
On the island, the Camping Vial Isla Pavón (tel. 02962/15-53-9168, US$3 per site) has electricity, clean toilets, and hot showers (US$0.65).
Despite its unappealing and unimaginative name, the spacious motel-style rooms at 
Hotel Sur Atlantic Oil (RN 3 Km 2404, tel. 02962/49-7008, US$37 s or d), part of the YPF gas station complex, fill up early (and it does not take reservations). Popular with southbound travelers, it also has a remarkable restaurant with particularly choice pastas (take lunch in the restaurant proper, rather than the adjacent confitería).
Across the highway, the new Hotel Río Santa Cruz (tel. 02962/49-7245, h_riosantacruz [at] yahoo [dot] com [dot] ar, US$43 s or d) is a good backup choice. Isla Pavón’s municipal hostería, usually the best option here, has been closed for renovation.
Northbound and southbound services along RN 3 use the Terminal de Ómnibus (Ibáñez Norte 130), but it’s also possible to flag down buses on the highway.
In summer, Transporte Las Lengas (tel. 02962/49-3023, laslengaselchalten [at] yahoo [dot] com [dot] ar) offers a daily 2 p.m. service to the El Chaltén [5] sector of Parque Nacional Los Glaciares [6] (6 hours, US$29).
Links:
[1] http://www.moon.com/destinations/argentina/southern-patagonia/coastal-santa-cruz-province/parque-nacional-monte-leon
[2] http://www.moon.com/destinations/argentina/southern-patagonia/coastal-santa-cruz-province/puerto-san-julian
[3] http://www.moon.com/destinations/argentina/southern-patagonia/coastal-santa-cruz-province/rio-gallegos
[4] http://www.moon.com/destinations/argentina/southern-patagonia/interior-santa-cruz-province/el-calafate
[5] http://www.moon.com/destinations/argentina/southern-patagonia/interior-santa-cruz-province/el-chalten
[6] http://www.moon.com/destinations/argentina/southern-patagonia/interior-santa-cruz-province/parque-nacional-los-glaciares