Zuzana/Seven Key's place in one word - wow.
With interior design and aesthetics more akin to a chic, mid-tier luxury hotel, we were legitimately pleasantly surprised at how beautiful the place was when we checked in slightly after the New Year.
It's every bit as beautiful as you see in the pictures, perhaps even more. Space-wise, it's extremely spacious for two (possibly even 3-4 with the pull-out sofa bed). They have designed the layout of the duplex superbly, which you'll understand once you get some time to explore the place and realize just how much is hidden away or how living spaces are separated smartly by storage/walls etc.
Amenities-wise, it has everything you need for your stay. Probably wouldn't be exaggerating if I said that it has nearly everything for one to move-in permanently. From a relatively well-equipped kitchen (electric stove, dishwasher, WiFi kettle, microwave etc) to a washer/dryer, smart lighting, smart TV, double-length master bedroom toilet for two etc. Being able to log-in natively on the smart TV into Netflix etc helps one feel so much more at home when travelling.
Location-wise, again you are right in the heart of Prague 1. The duplex shares a building with multiple restaurants and even a hotel. A modern, four-story shopping complex with western brands (and three supermarkets) is a two minute walk away. Everything else like Old Town Square, Wenclesas Square etc is a short walk away. Charles Bridge/Prague Palace etc are all easily accessible too.
Highly, highly recommended.