Marble outdoor to internal hardwood. House built in the 60's and i just spent ages clearing up old carpet tack and cement some dickhead had slapped over the floorboards.

It's not even, but hangs around 3cm difference between flooring surfaces. The surrounding walls are original bullnose sideboards in spectacular condition, so would like to be sympathetic.

Ideas? Suggestions?

(Yes i'm treating the rot and putting in a moisture break between the cement and wood)