Although the apartments are situated just a 5 minute walk from the main train station, there's no direct link by train from Tegel airport, so we took a cab which cost about €20.
We arrived at 12pm and as our room wasn't ready, we checked in and dropped our bags off and headed out sightseeing as a lot of the main sights are within walking distance of the apartments.
When we returned, our room was ready and our bags had been taken up. Although we originally booked a studio, they had given us a one bedroom apartment on the 6th floor, from which we could see the Reichstag dome. It was spacious and clean, with everything that you could need. Although, our only complaint would be that the air con did not go cold enough and blew out warm air, which was no good on a hot weekend.
We visited the pool a few times during our trip which was spotless and ideal to do a few lengths in after sightseeing. Towels and robes were provided.
We would definitely stay here if we visited Berlin again!