Just a short, pleasant walk down the hill from the Palacio da Pena are the Moorish Castle ruins.  A Portuguese tourism website says:

"Constructed by the Moors in the 8th or 9th Century A.D., this castle is situated on two peaks of the Serra de Sintra, and from its walls there are magnificent views. Surrounded by walls and several towers. It underwent various repairs, particularly in the Romantic period (about 1860), when King Consort Fernando of Saxe Coburg-Gotha restored it, afforested the surrounding areas and gave the ancient ruins new dignity."

Lyn conquers the heights

So do Janet and Bill

Bill actually climbed to the top of Mt. Moor

View from the castle

Resting for a moment

Another view

And another

Still another

Castle in the woods

Castle walls

The ocean view is clearer here

See the chimneys above the kitchen at the Palacio Nacional?

Resting again

Holding up the wall

Just try to conquer this place

Holding on tight

OK, that's enough castle