Crownhill Fort, built in 1863, is another Palmerston fort. It was built as part of the ring of defenses around Plymouth. Restored by the Landmark Trust, it is now home to several small businesses, event spaces, a Museum and a holiday apartment sleeping up to eight people.
Crownhill Fort is open to the public on the last Friday of each month when the grounds are open from midday with a tunnel tour at 3pm and a cannon firing at 5pm. See their website for more details.