Located high above the up-market shopping streets of Kolonaki, Dakis Joannou's art-filled Periscope Hotel urges guests to explore their thoughts on modern-day surveillance. There are 21 refreshingly minimal bedrooms and suites, including a penthouse with an open-air hot tub and 360° views of the city. Downstairs in the ground-floor bar, guests can use TV screens and a specially designed joystick to view images from a periscope mounted on the roof.