When asked what possessed him to assault Mount Everest, British climber George Mallory uttered the immortal phrase, "Because it's there." Eight decades later, Mallory's words resonate with lovers of the outdoors enticed by those lofty convex shapes. Whether it's a mountain or hill, whether we breeze or trudge up it, whether we prize the arrival at the top or the journey getting there, the scent of the ascent is irresistible.

Now that August's triple-digit mercury is behind us, we East County hikers can once again indulge our taste for the Up Staircase without risking a coronary event. For you who enjoy feeling your calves burn, lungs rasp and heart pound in your ears, I recommend two vertical adventures to test your mettle and reward you with splendid scenery.

Although not the equivalent of scaling the sheer face of El Capitan, these trails are, shall we say, rigorous. When in doubt, consult your physician before accepting the challenge.

Vista Grande Trail at Los Vaqueros

This is no ordinary hill. From it, looking eastward, I can see a hundred miles across Central Valley to the purple ripple of the Sierra, its peaks glazed in white. Turning south, I gaze down at the 1,500-acre Los Vaqueros Reservoir, its waters shaded from the newly risen sun by hills of gold vaulting above its eastern shore. The horizon beyond Livermore, 25 miles distant, is dominated by the ridge of Ohlone Wilderness veiled in the haze of dawn.

From this hill I can see all these things – and I'm only halfway to the top.

If the 1,272-foot crest of the Vista Grande Trail delivers what the name promises – a grand view – the trip to the tip delivers a grand test of a hiker's intention not to break stride. Veteran runners will tell you that Los Vaqueros/Vista Grande, per unit of measure, is one of the toughest hills in the Bay Area.

Less than a quarter mile up the road to the dam from the Interpretive Center is your jumping-off point, marked Los Vaqueros Trail. Stretch out, take a deep breath and start moving up in the world.

Look for the Vista Grande Trail intersection and head right. Your goal is a cluster of benches at the top. The brevity of this climb makes for a convenient and objective gauge of fitness. If you can hike to the top in less than 18 minutes, you're laying serious rubber. (Those freaks we know as runners will set their own standards.)

From the crest, hook up with Eagle Ridge and Oak Savannah trails for a view from the valley. For a shorter and more shaded stroll, the intimate Mariposa Canyon is your ticket home.

Olympia Summit at Mt. Diablo

By the time you begin your final assault of Mt. Diablo's 2,946-foot Olympia Summit, you'll have been climbing for 90 minutes. You should be sufficiently warmed up.

Trust me, you'll get warmer.

Mt. Olympia Road cuts along the northwest side of the summit, revealing the chaparral splendor of Wild Oat Canyon to the south. As you take a final curve leftward and upward, look to your right for the remains of a tree stripped naked by lightning. This is the starting point for your 600-foot push to the pinnacle. Twelve minutes is a number worth shooting for.

We won't elaborate on the glorious misery of the act of hauling your butt to the summit, except to say that the middle segment of the home stretch is the most grueling. Don't look up. It'll only discourage you.

At the top, however, the reward is obvious: a commanding view of the Bay Area. You can trace the waters of San Pablo Bay all the way to the wildlife refuge in Sonoma County. The east peak of Mt. Tamalpais (a paltry 2,571') anchors the coastal range in Marin County. And you can easily spot the Sutro Tower rising from the center of San Francisco. Only Mt. Diablo's North Peak (3,557') and Summit (3,849') obstruct your view south.

When you've had your fill of all this purple mountain majesty, a warning: don't go back down the summit the way you came up. You'll find yourself slip-sliding away – not walking – down such a ridiculous incline. Just below the summit, hang a right on the Zippe (no joke) Trail, which switchbacks down to Mt. Olympia Road. From there you can double back and try to beat your previous time to the top. Or you could head back home ... but where's the fun in that?