On March 23, 1912, the Cambridge subway opened from Harvard Square to Park Street Under. Park Street Under was built with two tracks with one side platform each and a center island platform, intended as a Spanish solution setup to speed boarding. Stairwells were added to the original platform level to connect to the lower level platforms. Unlike most other underground stations on the system (which were cut and cover construction with low ceilings), Park Street Under featured a spacious double-vaulted ceiling.