What is the name of Coba's tallest pyramid?

Coba’s tallest pyramid is called Nohoch Mul.

Nohoch Mul is the largest and best-known pyramid at the ancient Maya city of Cobá in Quintana Roo, Mexico. Its name comes from Maya and is commonly translated as “great mound,” an appropriate description for the massive stepped structure. The pyramid rises about 42 meters, or 138 feet, making it one of the tallest Maya pyramids in the Yucatán Peninsula and the tallest major Maya structure in that region.

The pyramid was built in stages and has a broad stepped base with a central staircase leading toward a temple at the summit. Its construction and use span the Classic and Postclassic periods, reflecting Cobá’s long history as a major political and economic center. Cobá was especially important for its extensive network of raised stone causeways, known as sacbeob, which connected the urban center with outlying settlements and neighboring sites.

Nohoch Mul is sometimes confused with famous pyramids elsewhere in the Maya world. El Castillo usually refers to the pyramid at Chichén Itzá, Temple I is the celebrated funerary pyramid at Tikal, and Caana is the tallest structure at Caracol. Those names belong to different Maya cities; for Cobá, the canonical answer is Nohoch Mul.