Learn Turkish: Bu sokakları adımlamayalı yepyeni binalar yaptılar. - Since I last walked these streets, they built brand new buildings.

It is formed from the verb adımlamak (to walk or pace) + the negative suffix -ma + the buffer -y- + the suffix -alı (since). Literally meaning 'since not walking,' this negative structure is the standard way in Turkish to express 'since [someone] last did' something or 'in the time since [someone] did' something.

There is no personal ending on adımlamayalı. How do we know it means 'since I last walked'?

The converb -(y)alı does not take personal endings. Its subject must be inferred from context. Here, the main clause is yaptılar (they built). Because the speaker is the one observing the changes in the streets, context strongly implies the subject of the walking is 'I' (or possibly 'we').

What is the root of the verb adımlamak?

It is derived from the noun adım (step). Adding the verb-forming suffix -la turns it into adımlamak (to take steps, to pace, or to walk around an area).

How is the word yepyeni formed?

This is an emphatic adjective created through reduplication. You take the first syllable of yeni (new) which is ye, add the consonant p, and attach it to the front of the original word. This intensifies the meaning from 'new' to 'brand new'.