Coast Redwoods, or Sequoia sempervirens, are the tallest species of tree on Earth. They are native to Coastal Northern California, but definitely not to the Sacramento Valley. However, we have planted them in Davis anyway, as they make quite an impressive skyline and provide a lot of shade. Redwoods can be seen throughout Davis in people's yards, various city parks and at several locations within the UC Davis campus. In the hot summers, they require a lot of water to survive the local climate.
There's a whole grove in the UC Davis Arboretum with some nice benches to sit under, as one in Putah Creek Park.
Standard disclaimer: These are not the same as the redwoods in the Sierra Nevada. Those are Sequoiadendron giaganteum(Giant Sequoia), the largest trees in the world.
See also: Town Flora