Although A Well Known Shape,

and building,

I can not think of any other famous buildings that are pentagon shaped, until I came across this one, 

Villa Farnese, a 16th century pentagonal Renaissance mansion,

it is built on foundations in the town of Caprarola, Viterbo, Northern Lazio, Italy, if you are in Rome it would be a great day out,

the Villa Farnese, also known as Villa Caprarola, is in the town of Caprarola in the province of Viterbo, Northern Lazio, Italy, approximately 50 kilometres north-west of Rome, as an aside do not confuse it with the Palazzo Farnese and the Villa Farnesina, both in Rome, photographs Villa Farnese,

and for anyone wanting a day out, here is the map,

Visiting hours:  Tuesday to Sunday from 8:30 am to 7:30 pm (last admission 6:45 pm). The park closes one hour before sunset.

On Sundays the park is closed, the Giardini Bassi can be visited.

Closed : Monday, January 1, December 25, except for extraordinary openings on the MiBACT project as per  DM 330 06/30/2016,  criteria for opening to the public, surveillance and safety of state museums and cultural sites.

Ticket: full € 5.00, subsidized € 2.00 (from 18 to 25 years old), subject to the concessions provided for in the entry regulations for Italian cultural sites, which can be consulted on the MiC website.