Tagaytay–Calamba Road

The Tagaytay–Calamba Road is a two- to four-lane, secondary and tertiary road in Laguna and Cavite, Philippines. Albeit discontinuous, it connects the city of Calamba in Laguna and the city of Tagaytay in Cavite. The road's missing link that will connect its Tagaytay and Calamba sections is under construction.

The segment of road from its western terminus at Tagaytay Rotonda to Ligaya Drive, both in Tagaytay, forms part of National Route 421 (N421) of the Philippine highway network, while the rest of the road remains unnumbered.

Tagaytay
The road starts at the Tagaytay Rotonda, a four-way roundabout with Aguinaldo Highway, Tagaytay–Nasugbu Highway, and Tagaytay–Talisay Road in Tagaytay City. It runs east along the Tagaytay Ridge. Various restaurants, hotels, residential developments, and tourists attractions could be found along this road. It then intersects the Santa Rosa–Tagaytay Road, which provides access to the South Luzon Expressway, and Ligaya Drive, where N421 turns towards Talisay, Batangas and the road transitions from a secondary road to a tertiary road. It then climbs Mount Sungay and terminates at the People's Park in the Sky. The entire Tagaytay segment is also known as Isaac O. Tolentino Avenue.

Calamba
The road continues at the southwestern boundary of Calamba, Laguna, running east from the northern gate to Tagaytay Highlands. Entirely a tertiary road, it is divided and locally known as Bunggo Road, Burol Road, Lawa–Punta Road, and Barandal Road, after the barangays it traverse through, respectively. It also traverses residential subdivisions and Calamba Premiere Industrial Park. It crosses beneath the South Luzon Expressway before terminating at Manila South Road (Old National Highway) in barangay Parian.

History
The road was built with its initial segment from Highway 17 (present-day Aguinaldo Highway and Tagaytay–Nasugbu Highway) to Mount Sungay at the eastern part of Tagaytay. Based on a 1941 map by the United States Coast and Geodetic Survey, it was supposed to connect Tagaytay to Santo Tomas, Batangas, but the plan did not materialize as it was later apparently realigned towards Calamba, Laguna, thus assuming the name Tagaytay–Calamba Road.

On March 15, 2017, Representatives Abraham Tolentino (Cavite–7th) and Celso Lobregat (Zamboanga City–1st) filed House Bill No. 4947 that seeks to rename the road's existing Tagaytay segment in honor of Isaac Tolentino, the former's father who served as Tagaytay mayor from 1954 to 1980 and died in 2016. On March 12, 2018, the Senate unanimously passed the bill's Senate counterpart that was sponsored by Senator Manny Pacquiao. On June 29, 2018, President Rodrigo Duterte signed Republic Act No. 11046, officially renaming such segment to Isaac O. Tolentino Avenue.