El Leoncito National Park

El Leoncito protects a stretch of high desert on the eastern slope of the Andes where the air is exceptionally dry and clear, with more than three hundred cloudless nights a year, and that quality of sky is why the park exists in its present form. Two observatories sit within it: CASLEO, with a 2.15 metre telescope, the largest in the country, and the Carlos U. Cesco station, which has spent decades charting the southern sky. Both run daytime tours and evening observing sessions for visitors. The land itself is worth the trip too, rising from desert scrub through canyons to high grassland, with guanacos, condors and a waterfall walk at El Rincón, and the ruins of an old estancia near the park entrance.

What you actually see

• CASLEO observatory - Argentina's largest telescope, open for tours and night sessions.
• The Cesco station - the older astronomical station on the ridge.
• The desert trails - walks to the El Rincón waterfall and through the canyons.
• The wildlife - guanacos, foxes and condors in open country.

When to go

March to November for stable skies and comfortable days; summer afternoons are hot and occasionally stormy. Night sessions require booking well ahead and run in clear weather only. Moonless nights show far more.

Honest expectations

Observatory visits are strictly scheduled and can be cancelled by weather or maintenance, so turning up unannounced usually fails. Nights at altitude are very cold, even in summer. The park's daytime landscape is austere rather than spectacular.

Nearby

Pampa El Leoncito and Barreal lie north in the same valley.