Hi
Berlin is very 'walkable' as it is flat, but it is HUGE...
You can get 1 or 2 day tickets for the red open-top tourist buses, with English descriptions, (do the complete circuit first, then jump on & off as you please) a quick way of seeing the core city.
You can get a 2 hour, or 1/2/4/7 day public transport tickets good for U Bahn, S-Bahn, & busses (not red Tourist) good when you know where you are going (buy at airport kiosks or Tourist Info Offices)
The 'Museum Island' is essential for Art Nuts & the TV tower has good views (long queues, book in advance if possible)
Checkpoint Charlie Museum & very close to the Topography of Terror, Topographie des Terrors, with a large part of the East/West Wall. This is opposite to the former Luftwaffe department.
Lots of BERLIN Museums Here
The Militärhistorisches Museum Flugplatz Berlin-Gatow is an obvious one
Dresden, my all Time Favourite City, been 17 times...
The Saxon Kings' Pleasure City, the core tourist bits are very walkable in the 'Old town', but the Red Tourist Bus Dresden advice applies, Theaterplatz, 01067 Dresden.
Dresden Museums Here Dresden Armory & Dresden Transport Museum are near the Dresden Frauen Kirche, and many many more...
Galerie Neue Meister, with Klimt, Kirchner, Otto Dix, Casper David Friedrich as my personal Art Nut Favourite.
The Bundeswehr Military History Museum whimsically sliced by Liebeskind, is in the North of the Newtown. This one is worth at least 1/2 a day, as are the others...
Enjoy.