Lake Merritt is located smack in the middle of downtown Oakland.
Consider this a crash course on the history of Lake Merritt in general before I move on to particular sites surrounding the lake. Originally a tidal estuary called San Antonio Creek, or the San Antonio Slough, it served as a point of access for ships to carry supplies between San Francisco and the East Bay. Beginning in 1852, with the incorporation of the city of Oakland, various improvements changed the size and nature of the lake to its current state. The lake was formally created in 1867 when Mayor Samuel Merritt donated 155 acres of privately owned tidal marshland to the city in order to create a public waterway. At this point the estuary was an uncontrolled tidal flat that experienced significant daily tides and was surrounded by mudflats. In 1869 Samuel Merritt donated money to begin the construction of a dam and bridge across the estuary at 12th st. This bridge replaced an earlier toll bridge between downtown Oakland and the Brooklyn township and served to control the tides and isolate the lake from the San Francisco bay. The construction of the dam also included a 3.18 mile long cement retaining wall surrounding the lake.
In 1870, Lake Merritt became the first national wildlife refuge, both to protect the migratory birds that nested there as well as protect the residents from the dangers and noise of hunting firearms being used within city limits. By the 1890s, as the city continued to grow, the lake was being used as a public sewer with approximately 90% of the city's sewers draining directly into it. Throughout the 20th century the city would deal with occasional problems related to health, foul odors, and water pollution. The lake was filling with sewage and runoff from the city so quickly that the city had to begin a program to regularly dredge the lake and remove excess material. In 1907 the material dredged from the lake was used to fill in the mudflats surrounding 12th street, further isolating the lake from the waters of the bay. In 1922 the material removed from the lake was used to create the first of five bird islands near the bird sanctuary. The city continued to develop park land and features surrounding the lake throughout the latter half of the 20th century, but it wasn't until the 1980s that effective solutions to water pollution and raw sewage leaking into the lake were put into place. Since then, the cleanliness of the water has improved significantly and the overall health of the lake has improved.
I like Lake Merritt a lot and, on a sunny morning, there's really not a better way to cut through central Oakland on my bike ride to work. The parks surrounding the lake see heavy recreational use and there's always herds of joggers and walkers out on the paths. There are dozens of great local historical sites within an easy ride of Lake Merritt and they're all worth a visit. Children's Fairy Land, the El Embarcadero promenade, the Alameda County courthouse, and the Bellevue-Staten Building are all prominent landmarks. The Tribune Tower, all of the site in Jack London Square,and the historical homes surrounding Preservation Park are an easy bike ride away as well.
Getting There By Bike...
Lake Merritt is located in central Oakland and it's hard to miss. Since it's shoulder-to-shoulder with the downtown business district there's any number of ways to get to the lake proper. Remember that the streets that surround Lake Merritt can be filled with heavy car traffic at rush hour. There are excellent bike lanes surrounding the entire lake, but if you're at all hesitant about riding in traffic then it might be best to consider riding on the multi-use path that runs along the water. If you're going to use the multi-use path, invest in a bell for your bike since you'll be calling out to pass joggers and walkers very frequently. The neighborhoods surrounding the lake bear exploring, but the lake is close enough to downtown Oakland that it's best if you invest in a proper bike lock before you leave your bike unattended.