Fluent speakers of English, could you help me with my English?

I am translating a very complex book about architecture (this chapter is about famous architect Mies van der Rohe and his Seagram Building) and there are phrases that I find difficult to understand. What does the following phrase mean 'as a compliment to' (also, does the word 'concession' that occurs later in the paragraph means the same as 'compliment'?)

In this bronze and brown glass office tower, Mies once again achieved that Semperian interweaving of fenestration with structure. This time, however, unlike Lake Shore Drive, he created a frontalized axial composition facing a granite piazza, the slab itself being set back some 27 metres (90 feet) from the building line, as a compliment to the 1917 Racquet Club by McKim. Mead and White on the other side of Park Avenue. This concession on the part of the client enabled Mies to achieve his once and only monument in Manhattan, and to rival, in grandeur, the one New York structure that he had long since admired, the George Washington Bridge.