As was once said about another ruined estate "the house now possesses as a ruin a nobility it did not possess when intact." When the weather gets a little less humid I plan on taking one of the state-sanctioned kayak tours.
Another great 'ruined' Hudson Valley estate is (or perhaps was) Rhinecliff, the J.J. Astor residence up beyond Rhinebeck. The 1912 house was demolished ca. 1940 and replaced by a smaller home, however, the McKim Mead and White sports complex from John Jacob Astor's era remained in excellent condition last time I visited. The real charm, however, lay in the unrestored, decaying, service structures left from the Edwardian Era. Have not been there in years and would be disappointed to learn that they have either been demolished or over restored.
Similarly, the unrestored, ill repaired 'not part of the tour' buildings at the Frederick Vanderbilt estate down river a bit from the Astor site were considerably more interesting than the mansion.
A few miles further down the road, and hidden away in the woods is/was a towered 50 room Italianate monster of a Victorian Estate which, last time I was there, was as impressive a ruin as Bannerman's. The interior had largely collapsed leaving the brick facade an interesting shell. The way things have built up in the 16 years since I've trekked there, I'm fairly sure the site is now either an office park or a "Luxury Housing Estate."
Further up river, 'though not a ruin per se, is the Swallow House- a ca 1846 residence in Valatie NY, constructed from the remains of a fatal shipwreck. The Swallow was an early Hudson River steamboat which grounded on a rock back in 1845 and then broke in half, the stern section sinking and killing either 15 or 25 passengers. The forward half was apparently hauled ashore, broken up, and converted into the house which -as a boy- held endless fascination for me. Have not been there since ca. 1980 and am not sure I want to go now, since there is the distinct possibility that it has either been demolished or, worse,
'aluminum sided.'*
*since I wrote that, I have learned that the house is still there, in excellent repair, and that portions of the interiors, which I did not see as a boy, are also from the lost riverboat and include her spiral staircase. I sense a potential article in this.....