  Based on a hydrodynamical model, we compare 130 GeV/$A$ Au+Au collisions at
RHIC and 17 GeV/$A$ Pb+Pb collisions at SPS. The model well reproduces the
single-particle distributions of both RHIC and SPS.
  The numerical solution indicates that huge amount of collision energy in RHIC
is mainly used to produce a large extent of hot fluid rather than to make a
high temperature matter; longitudinal extent of the hot fluid in RHIC is much
larger than that of SPS and initial energy density of the fluid is only 5%
higher than the one in SPS. The solution well describes the HBT radii at SPS
energy but shows some deviations from the ones at RHIC.
