The famous railway bridge designed by Isambard Kingdom Brunel engineered by Mo Browne.
Boulter's Lock and Boulters Island on the River Thames. A great spot for walks amongst relatively tame squirrels and views of Maidenhead Wier. There is also a small hotel/restaurant on the Island.
You can shoot the squirrels from there.
Cookham is a picturesque village between Maidenhead and Marlow. It is a traditional English country village with a hugely popular gallery and excellent but expensive restaurants. Trains link Cookham with Maidenhead every hour. Alternatively walk there along the River, about 1 hour.
Or swim, about 3 hours front crawl, allow 7 for backstroke.