Dowgate was one of the many small docks on the north bank of the Thames. It is now just upstream of Cannon Street railway station.
The overlays that highlight 17th century London features are approximate and derived from Wenceslaus Hollar’s maps:
Open location in Google Maps: 51.509527, -0.091732
Dowgate Stairs and Wharf are on the London side of the Rocque map
Chart showing the number of references in each month of the diary’s entries.