Finding the "most recent" rows

I have a table (representing a set of observations) with datetime fields and a
non-unique place field.

e.g.
create table obs (
the_time datetime,
the_place char(8),
...other fields...
)

I'd like an efficient way to pull out the most recent row (i.e. highest
datatime) belonging to *each* of a number of places selected by a simple
query.

e.g. given a table such as:

the_time the_place ...
0910 London
1130 London
0910 Paris
0930 London
0840 Paris
1020 London
0740 Paris

I'd like to select:
1130 London
0910 Paris

Most of my attempts at this (as an SQL novice) feel very clumsy and
inefficient. Is there an efficient way of doing this in SQL?
--

Julian Scarfe