Globular and nuclear clusters are ideal nurseries for black holes (BHs) and other compact stellar remnants and are sufficiently crowded to favor the formation of tightly bound pairs, which in some cases can merge and release observable gravitational waves. Globular clusters are thought to be a perfect birthplace for intermediate mass BHs (IMBH, mass range 10^2-10^5Msun), while some nuclear clusters offer a unique view on the interplay between stars and supermassive BHs (SMBH, mass range 10^5-10^9 Msun). Unfortunately, defining a robust way to assess the presence of these compact objects in dense clusters on an observational basis is a hard task to accomplish. In this talk, I will discuss the impact of stellar BHs and IMBHs evolution on globular and nuclear clusters observational properties. For globulars, it is possible to define a ``fundamental plane'' that connects their observational quantities to the main properties of their BH populations. This fundamental plane suggests that ~30 Galactic globular clusters may be currently harboring a noticeable number of BHs. Regarding nuclear clusters, I will discuss how the processes that govern their formation can be connected to observations using our Galactic Centre as a reference case.