The apartment of Lenka's apartment is awesome. It's two minutes away from Charles bridge but in a quiet lane. So you are in the midst of action yet cut off. There are plenty of places to eat and drink close by and even a small supermarket. Bonus is the Shakespeare bookstore around the corner :)
The apartment itself was smaller than what I expected. It's good for short stays but may feel cramped if you are planning to stay for many days if you're more than one person staying. But it's functional and very pleasant.
Lenka is very prompt in communication and we had no problem at all in coordinating our check in and check out.