Both are understood, but the more correct way would be "there WAS a monument..." :)

You can write 'There had been a monument before it was removed' or 'There was a monument before it was removed.' The past perfect is used to make it clear that one event happened before another in the past. John had gone out when I arrived in the office' (first John went out then I arrived in the office) 'There had been a monument before it was removed.' (first there was a monument then it was removed.) But when a sentence includes 'before' or 'after' it is possible to put both verbs in the past simple because 'before' and 'after' tell us which action happened first. 'I lived in london before I moved to Italy.' (before tells us that lived in London happened first) So you can say 'There was a monument before it was removed'. But you cannot say 'there had been a monument before it had been removed'.

"There had been a monument before it was moved" is correct. We use the past perfect to show something that happened further in the past than another thing in the past (which takes the simple past tense). So if it is now 11:00, and A happened at 9:00 and B happened at 10:00, we'd use past perfect to discuss A and simple past to discuss B (e.g., "The light bulb had been on nonstop for 32 days before it burnt out.").