This plant is a hybrid, between the large A. hippocastanum and a smaller red flowering buckeye (horse chestnut) A. pavia. You may be looking at the cultivar 'Briotii' which is generally the form available in the industry however, larger ones in our area all seem to have the lighter pink colored flowers.
The picture below is located on Opal Cliff.
Fruits are fun. The seeds are contained in a green fleshy husk with prickles. Was a 3 seeded capsule but only one seed matures. Seeds are the classic sling shot projectile, glossy browns and patterned. Seems that the fruit can be either smooth or prickled. These didn't produce any seeds, but you can see the overall shape and surface.
Here are the seeds from a fruit that has a smooth husk.
Trunks are large with smooth bark for years, eventually developing small fissures and often have rounded plates.
Other horse chestnuts without flowers. These are pink or red, and is a smaller tree with smaller leaves than those of A. hippocastanum, and the terminal leaflet is not obovate. Additionally, the terminal bud is not sticky.
621 Gilroy Dr. ('Briotii')
308 Grand (at the ocean end of Oakland Ave.)
4410 Opal Cliff Drive
Broadway near Ocean
221 Windham St is a beauty